18NA366

Bulletin No.:
Service Bulletin
Date:
18-NA-366
November, 2019
INFORMATION
Subject:
2019 Chevrolet Silverado 4500HD 5500HD and 6500HD New Model Features
Brand:
Model:
Chevrolet
Silverado
4500HD
Chassis-Cab
Silverado
5500HD
Chassis-Cab
Silverado
6500HD
Chassis-Cab
Model Year:
From:
Involved Country
Copyright 2019 General Motors LLC. All Rights Reserved.
To:
2019
United States
VIN:
From:
To:
—
Engine:
Transmission:
Duramax® 6.6L
V8 Diesel —
RPO L5D
Allison®
6-Speed
Automatic
(RPO Will Vary
by Vehicle and
Application)
Page 2
November, 2019
Bulletin No.: 18-NA-366
Overview
5122202
2019 Silverado 4500HD — Preproduction Model
Shown
Bulletin No.: 18-NA-366
November, 2019
Page 3
5136828
2019 Silverado 6500HD — Preproduction Upfitted
Model Shown
Bulletin Purpose
This purpose of this bulletin is to introduce the new
2019 Chevrolet Silverado 4500HD, 5500HD and
6500HD medium duty trucks. The bulletin will help the
Service Department Personnel become familiar with
the vehicle’s new Duramax® 6.6L V8 — RPO L5D
diesel engine, the Allison® transmission with an
available PTO option, brake system, chassis, and other
general information. These trucks are available
exclusively as chassis cab models, making them ready
for up-fitters to customize for the various requirements
of their customers. The trucks will be available in 2WD
and 4WD. They will be very connected, with options
that include OnStar®, Commercial Link, a built-in
OnStar® 4G LTE™ Wi-Fi® Hotspot (requires a paid
data plan), as well as wireless cell phone charging and
Bluetooth®. They also support the Apple® CarPlay™
software feature and Android™ Auto™ application.
They will be built in partnership with Navistar at its
Springfield, Ohio plant.
Additional highlights include:
5137314
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Preproduction image shown.
Clean top of rail design with no protruding welds or
brackets for smooth integrated upfits.
Robust, single-piece frame rail for enhanced
durability.
Factory-available rear air suspension.
Fuel tank capacity of up to 65 gallons (246 liters).
Page 4
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November, 2019
Bulletin No.: 18-NA-366
Painted chassis provides corrosion protection.
40/20/40 split-bench front seat
60/40 rear bench seat (Crew Cab)
Standard Grille Guard Screen for insect protection
is mounted behind the grille.
5156383
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Preproduction model shown.
Dual batteries with protective cover in place.
5134340
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Preproduction model shown.
Tilt engine cover design. Provides service
technicians with easy and comfortable access to
the engine.
5124232
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5181883
•
Preproduction model shown.
The dual batteries are located under the cab on
the driver side of the vehicle. An auxiliary
jump-start 12V positive stud with a protective
cover is located on the driver side of the vehicle
beneath the driver door and to the left of the
batteries.
Preproduction model shown.
Up to 50-degree wheel cut enhances turning
radius and maneuverability and also allows for
easier serviceability.
Bulletin No.: 18-NA-366
November, 2019
Page 5
5175908
•
Preproduction model shown.
Easy-to-reach control buttons. Available upfitter
switches, (4) provide 4-30 amp circuits to facilitate
installation of aftermarket electrical accessories
and are located on the instrument panel.
•
Some vehicles may be equipped with a
110/120-Volt Alternating Current power outlet. It
can be used to plug in electrical equipment that
uses a maximum of 150 watts. If equipped with a
center console, the power outlet is in front of the
cupholders. If equipped with bench seats, the
power outlet is on the center stack.
5170757
•
If equipped, the sunglasses storage compartment
is in the overhead console. Press the button on
the cover and release to access.
5182463
Page 6
•
November, 2019
The Oil Life Monitor calculates engine oil life
based on vehicle use parameters and displays the
percentage of Oil Life Remaining and Change
Engine Oil Soon on the DIC when it’s necessary to
change the engine oil and filter. The Oil Life
Monitor should be reset to 100% only following an
oil and filter change.
Available Models and Trim Level
The following Regular Cab and Crew Cab Models and
Trim Levels are available:
– Crew Cab: 2WD 1WT
– Crew Cab: 2WD 1LT
– Crew Cab: 4WD 1WT
– Crew Cab: 4WD 1LT
– Regular Cab: 2WD 1WT
– Regular Cab: 2WD 1LT
– Regular Cab: 4WD 1WT
– Regular Cab: 4WD 1LT
Wheelbase — Overall Length — Cab to Axle
5136912
The following are available:
– Regular Cab: Wheelbase: 141—243 inches (7)
– Regular Cab: Length: 224.5—360 inches (12)
– Regular Cab: Cab to Axle: 60, 84, 108, 120, 138,
150, 162 inches
– Crew Cab: Wheelbase: 175, 199, 235 inches
– Crew Cab: Length: 258.8, 282.8, 296.6, 344.2
inches
– Crew Cab: Cab to Axle: 60, 84, 120 inches
Brakes
Bosch TCS8TA Brake System
This vehicle is equipped with a Bosch TCS8TA brake
system which utilizes a Hydro-Max™ hydraulic brake
booster and master cylinder. The system uses DOT 3
Hydraulic Brake Fluid.
Bulletin No.: 18-NA-366
The Bosch® TCS8TA brake system provides the
following vehicle performance enhancement systems:
• Antilock Braking System (ABS).
• Electronic Brake Force Distribution (EBD).
• Drag Torque Control (DTC).
• Traction Control System (TCS).
Brake System Components
The following components are involved in the operation
of the brake system:
• Bosch® TCS8TA Hydraulic unit with attached
electronic brake control module (EBCM).
• The Body Control Module (BCM) monitors the
brake pedal position sensor signal and when the
brake pedal is applied it sends a high speed serial
data message to the EBCM indicating the brake
pedal position.
• The brake pressure sensor is used to sense the
action of the driver application of the brake pedal.
The sensor provides an analog voltage signal that
will increase as the brake pedal is applied. The
EBCM monitors the brake pressure sensor which
is integral to the brake pressure modulator.
• The instrument cluster displays the vehicle speed
based on the information from the engine control
module (ECM). The ECM sends the vehicle speed
information via a high speed serial data to the
BCM. The BCM then sends the vehicle speed
information via a low speed serial data to the
instrument cluster in order to display the vehicle
speed, either in mph or km/h based on the vehicle
parameter that is selected.
ABS
When wheel slip is detected during a brake application,
an ABS event occurs. During ABS braking, hydraulic
pressure in the individual wheel circuits is controlled to
prevent any wheel from slipping. A separate hydraulic
line and specific solenoid valves are provided for each
wheel. The ABS can decrease, hold, or increase
hydraulic pressure to each wheel. The ABS does not
increase hydraulic pressure above the amount which is
transmitted by the master cylinder during braking.
During an ABS braking event, a series of rapid
pulsations may be felt in the brake pedal. These
pulsations are caused by the rapid changes in position
of the individual solenoid valves as the EBCM responds
to wheel speed sensor inputs and attempts to prevent
wheel slip. A ticking or popping noise may also be
heard as the solenoid valves cycle rapidly. During ABS
braking on dry pavement, intermittent chirping noises
may be heard as the tires approach the slipping point.
These noises and pedal pulsations are considered
normal during ABS operation.
Bulletin No.: 18-NA-366
November, 2019
ABS Activation Sequence
The typical ABS activation sequence is as follows:
• Pressure Hold: The EBCM closes the isolation
valve and keeps the dump valve closed in order to
isolate the slipping wheel when wheel slip occurs.
This holds the pressure steady on the brake so
that the hydraulic pressure does not increase or
decrease.
• Pressure Decrease: If a pressure hold does not
correct the wheel slip condition, a pressure
decrease occurs. The EBCM decreases the
pressure to individual wheels as needed during
deceleration when wheel slip occurs. The isolation
valve is closed and the dump valve is opened. The
excess fluid is stored in the accumulator until the
pump can return the fluid to the master cylinder or
fluid reservoir.
• Pressure Increase: After the wheel slip is
corrected, a pressure increase occurs. The EBCM
increases the pressure to individual wheels as
needed during deceleration in order to reduce the
speed of the wheel. The isolation valve is opened
and the dump valve is closed. The increased
pressure is delivered from the master cylinder.
Drag Torque Control Operation
During a slip event, the EBCM can send a message to
the ECM to increase engine torque until the driven
wheels are turning at a rate appropriate to the vehicle’s
speed.
Electronic Brake Force Distribution Operation
The slip ratio of each of the vehicle’s wheels is
individually monitored. If any wheel starts to slip, the
brake pressure of each wheel can be modulated so that
the slip ratio remains within a safe range.
Page 7
from slipping. The EBCM commands the pump motor
and appropriate solenoid valves ON and OFF to apply
brake pressure to the slipping wheel.
Driver Information — Brake Warning Indicator
The instrument cluster turns the brake warning
indicator ON when the following occurs:
• The instrument cluster performs the bulb check.
• The BCM detects that the parking brake is
engaged. The instrument cluster receives a serial
data message from the BCM requesting
illumination.
• The EBCM detects a faulty pump motor, solenoid
valves, an internal hardware failure or a too high
or too low battery voltage and sends a serial data
message to the instrument cluster requesting
illumination.
Driver Information — ABS / TCS Indicator
The instrument cluster turns the ABS/TCS indicator ON
when the following occurs:
• The instrument cluster performs the bulb check.
• The EBCM detects a malfunction which disables
the ABS and sends a serial data message to the
instrument cluster requesting illumination.
• The driver manually disables the TC by pressing
the traction control switch. The EBCM sends a
serial data message to the instrument cluster
requesting illumination.
Parking Brake System
Hydro-Max™ Operation
The Hydro-Max™ is a hydraulically powered brake
booster which provides power assist for the hydraulic
brakes. A booster combined with a master cylinder
forms the hydraulic brake actuation unit. The booster
which is powered by the power steering pump reduces
the pedal effort required to apply the brakes as
compared to a non-power system. The hydraulic
booster has a backup pump which will provide
hydraulic boost at a reduced rate if the normal source of
fluid is interrupted. The master cylinder is a split system
type with separate fluid chambers, pistons and outlet
ports for the front and rear brake circuits. The master
cylinder includes a differential pressure switch and a
brake fluid level indicator switch.
Traction Control Operation
When drive wheel slip is noted, the EBCM will enter
Traction Control (TC) mode. First the EBCM requests
the ECM to reduce the amount of torque to the drive
wheels via a serial data message. The ECM reduces
torque to the drive wheels and reports the amount of
delivered torque. If the engine torque reduction does
not reduce drive wheel slip enough, the EBCM will
actively apply the brakes on the slipping drive wheel.
During TC braking, hydraulic pressure in each drive
wheel circuit is controlled to prevent the drive wheels
5169530
The parking brake is a driveline park brake system
consisting of a single drum design (1), mounted around
the propeller shaft and over the brake shoes, forward of
the rear differential. When the parking brake pedal is
depressed, the parking cable is pulled, overcoming
spring pressure within the parking brake and pushing
the brake shoes into contact with the inside of the
parking brake drum. When the operator disengages the
parking brake pedal, spring tension in the parking brake
pulls the park brake shoes to their
Page 8
November, 2019
original (disengaged) position. The parking brake
self-adjusts for brake shoe wear by using a star wheel
mechanism.
Bulletin No.: 18-NA-366
Driver Information Center (Up-Level)
Commercial Link
Overview
Commercial Link enables fleet account owners a better
system to manage their vehicles and improve overall
fleet efficiency. Commercial Link uses the built-in
OnStar® connectivity (must be active) to provide useful
vehicle data, such as maintenance notifications and
vehicle location, in order to better manage mileage and
expenses more effectively. GM is the only auto
manufacturer to offer an embedded vehicle
management solution. Commercial Link is a monthly
subscription with no annual contract. There is also the
option of signing up for invoice payment in increments
of 3 months, 6 months or 1 year.
Driver Information Center
5187070
The DIC displays are shown in the center of the
instrument cluster in the Info app. The displays show
the status of many vehicle systems. The controls for the
DIC are on the right steering wheel control.
Driver Information Center (Base Level)
Engine Duramax® 6.6L V8 — RPO L5D
Overview
5187065
The DIC displays are shown in the center of the
instrument cluster. The displays show the status of
many vehicle systems. The trip odometer reset stem in
the instrument cluster is used to access the DIC menu
items.
5122972
Engine Shown is 2018 Duramax® 6.6L V8 — RPO
L5P (L5D is similar)
The Duramax® 6.6L, V8 — RPO L5D is a turbocharged
diesel engine produced by General Motors for use in
the new 4500HD, 5500HD and 6500HD trucks. The
L5D is part of a new generation of Duramax® engines.
The engine is closely related to the Duramax® 6.6L,
V8 — RPO L5P engine, but is equipped with a smaller
turbocharger and different engine control module
calibrations.
Bulletin No.: 18-NA-366
November, 2019
Engine Features and Specifications
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Bore/Stroke: 4.055 inches (103 mm) /
3.8976 inches (99 mm).
Compression Ratio: 16.0:1
Cooling System: Cooling system flow capacity is
270 L/min at 3,172 RPM.
Connecting Rods: The connecting rods are
one-piece hot forged steel. The connecting rods
and caps are of a fractured split design to improve
durability and reduce internal friction. The
connecting rod small end is tapered cut for
reduced weight and improved durability.
Crankshaft: The crankshaft is a forged steel
design with five main bearings. Crankshaft thrust
is controlled by the number 5 bearing.
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Page 9
the ports are of a high swirl design for improved
combustion. The cylinder head gaskets consist of
an all steel laminated construction.
Emissions Controls: Cooled Exhaust Gas
Recirculation (EGR), Selective Catalytic
Reduction (SCR), Diesel Particulate Filter (DPF),
intake throttle.
Engine Covers: There is a front engine cover
and a flywheel housing, both are made of
aluminum. The full bell flywheel housing is cross
bolted to the upper oil pan. The flywheel housing
also supplies a crossover passage for engine
coolant. The front engine cover houses the gear
train and provides a mounting surface for the
cooling fan pulley assembly.
Engine Oil Capacity with Filter: Capacity is
10 qt (9.5L).
Exhaust Gas Recirculation: Exhaust gas
recirculation is water cooled for improved
reduction in NOx emissions.
Exhaust Manifold: The exhaust manifolds are a
1-piece cast iron design. The exhaust manifolds
direct exhaust gasses from the combustion
chambers to the exhaust system. Each manifold
has an externally mounted heat shield that is
retained by bolts.
Firing Order: 1-2-7-8-4-5-6-3
Fuel System: Direct injection with high-pressure
common rail. In the diesel engine, air alone is
compressed in the cylinder. Then, after the air has
been compressed, a charge of fuel is sprayed into
the cylinder and ignition occurs, due to the heat of
compression.
4663083
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Cylinder Block: The engine block utilizes a deep
skirt design for increased rigidity. The cylinders
are positioned in a 90 degree "V" orientation with
the number one cylinder being the right front. The
block is induction hardened for increased
durability. The crankshaft bearing caps are
cross-bolted to enhance structural rigidity.
Cylinder Head: The cylinder heads are made of
aluminum for lighter weight and rapid heat
dissipation. There are 4 valves per cylinder and
5152404
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Fuel Type: GM recommends the use of TOP
TIER Diesel Fuel to keep the engine clean and
reduce engine deposits. Use Ultra-Low Sulfur
Highway Diesel Fuel and/or B20 biodiesel. Fuels
Page 10
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November, 2019
with a biodiesel content up to 20% by volume may
be used (e.g., named B20). Look for the TOP
TIER Diesel Fuel Logo.
– Do not use diesel fuel with more than 15 ppm
Sulfur.
– Do Not Use Non-Highway Diesel Fuel.
Glow Plugs: The engine utilizes eight ceramic
glow plugs. Compared to conventional glow plugs,
ceramic glow plugs enable greater efficiency
through higher temperature capability and faster
preheating time. However, ceramic glow plugs are
much more sensitive to damage than conventional
glow plugs. Damage can occur to the glow plug
and not be visible, causing future engine failure.
Therefore, ceramic glow plugs are considered
one-time-use. Be sure to discard and replace with
NEW whenever a ceramic glow plug is removed
from the cylinder head. If the cylinder head is ever
removed with the ceramic glow plugs, the ceramic
glow plugs must all be replaced with new.
Whenever installing a new ceramic glow plug,
clean the glow plug bore with a proper tool as
outlined in the service procedure. Carbon build-up
in the glow plug bore can damage the ceramic
glow plugs.
Governed Speed: 2900 RPM
Horsepower: 350 hp (257 kW) @ 2700 RPM.
Torque: 700 lb-ft (949 Nm) @ 1600 RPM.
Intake Airflow Valve: The intake airflow valve is
a throttle plate actuator and is used to achieve
high exhaust gas recirculation rates. It increases
the pressure difference between exhaust and
intake so that the appropriate exhaust quantity
can be mixed with the intake air.
Maximum Braking Speed: 4,800 RPM.
Maximum Powered Speed: 3,450 RPM.
Oil Cooler: The oil cooler lowers engine
temperature by cooling the oil with engine coolant.
Engine coolant is directed from the water pump to
the oil cooler by a coolant tube. The oil filter
attaches directly to the oil cooler.
Oil Pump: The oil pump is gear driven directly
from the crankshaft. The oil pump drive gear is a
slip fit to the crankshaft.
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Bulletin No.: 18-NA-366
Piston: The pistons are a full-floating design. The
piston pins are a slip fit in the bronze bushed
connecting rod and are retained in the piston by
round wire retainers. The pistons have a piston
cooling oil channel cast inside of the piston. These
cooling oil channels utilize an oil jet located at the
bottom of the cylinder bore to direct oil into the
piston channel. There are two compression rings
and one oil control ring. There is a groove
machined into the pistons between the first and
second compression rings. This groove reduces
compression ring leakage by providing an empty
space for expanding gases, reducing the
combustion gas pressure on the second
compression ring.
Turbocharger: The turbocharger is water cooled
for improved durability. It is a variable vane style.
The pitch of the turbine vanes can be changed by
ECM command to meet varying conditions.
Upper Oil Pan: A single piece cast aluminum
upper oil pan contributes to crankshaft and block
rigidity while reducing overall weight.
Valvetrain: The engine utilizes a mechanical
roller lifter for valve operation. One rocker arm
operates two valves simultaneously through a
valve bridge.
Water Pump: The water pump is gear driven for
improved reliability.
Elevated Idle
The engine has a cold temperature high idle feature
which elevates the engine idle speed from base idle to
1050 to 1100 RPM when outside temperatures are
colder than 32°F (0°C), and the engine coolant
temperature (ECT) is colder than 150°F (65°C). This
feature enhances heater performance by increasing the
ECT faster.
Engine Block Heater
If equipped, the engine block heater can provide easier
starting and better fuel economy during the engine
warm-up period in weather conditions that are colder
than 0°F (−18°C). Vehicles with an engine block heater
should be plugged in at least four hours before starting.
An internal thermostat in the plug-end of the cord may
exist, which will prevent engine block heater operation
at temperatures warmer than 0°F (−18°C).
Bulletin No.: 18-NA-366
November, 2019
Page 11
Fuel System Overview
L5D Fuel System Diagram
5135268
Legend
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
Secondary Fuel Tank (if equipped)
Fuel Filter with Water in Fuel Sensor
Fuel Heater
Fuel Temperature Sensor
Fuel Pressure Sensor
Exhaust Aftertreatment Fuel Injector (not
equipped on the L5D)
Dual Fuel Rail Pressure Sensor
(Contains Fuel Rail Pressure Sensor 1
and Fuel Rail Pressure Sensor 2)
Fuel Rail Assembly
The primary fuel tank and secondary fuel tank (if
equipped) stores the fuel supply. A fuel transfer pump is
located in the secondary fuel tank to transfer fuel to the
primary tank. The primary fuel tank contains a 3–phase
electric fuel pump that is controlled by the fuel pump
driver control module and ECM. Fuel is pumped from
the primary fuel tank through the fuel feed line to the
fuel filter assembly. The fuel filter assembly consists of
a fuel filter/water separator, fuel heater, fuel
temperature sensor, and a water in fuel sensor. Fuel
flows out of the fuel filter assembly through the rear fuel
feed pipe and past the fuel pressure sensor to the fuel
injection pump. High pressure fuel is supplied through
the high pressure fuel line to the fuel rails and then
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
Fuel Rail Pressure Regulator 2
Fuel Pressure Regulator 1 (Located in
Fuel Injection Pump)
Fuel Injection Pump
Fuel Injectors
Primary Fuel Tank
Electric 3–Phase Fuel Pump
Fuel Transfer Pump (if equipped with
secondary tank)
Fuel Pump Driver Control Module
through the fuel injector lines to the fuel injectors. High
pressure fuel is controlled by the ECM, Fuel Pressure
Regulator 1 and Fuel Pressure Regulator 2. Excess fuel
returns to the fuel tank through the fuel return pipes.
Exhaust Aftertreatment Uses Post Injection
The engine uses post combustion injection through the
engine fuel injectors to increase the exhaust gas
temperature as needed for regeneration. It does not
use an HC Injector.
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November, 2019
Bulletin No.: 18-NA-366
Engine Oil
Exhaust Brake
Specification
Engine oil with the letters CJ-4 or CK-4 are required for
the Duramax® 6.6L diesel engine. The CJ-4 or CK-4
designation can appear either alone or in combination
with other American Petroleum Institute (API)
designations, such as API CJ-4/SL. These letters show
API levels of quality.
Operation
The exhaust brake can be used to enhance the vehicle
brake system and reduce brake lining wear. Downshifts
may be automatically selected to increase engine
speed, which increases the effectiveness of the
exhaust brake. The number of downshifts selected is
determined by the length of time the brakes are applied
and the rate the vehicle is slowing. The system delivers
the correct amount of braking to assist in vehicle
control. The heavier the vehicle load, the more active
the engine exhaust brake will be. Automatic downshifts
will not occur if the vehicle is in Range Selection Mode.
American Petroleum Institute (API) Symbol
Activation
5123610
This doughnut-shaped logo (symbol) is used on most
oil containers to help you select the correct oil. It means
that the oil has been certified by the American
Petroleum Institute. Look for this on the oil container,
and use only those oils that display this logo.
Caution: Use only engine oils that have the
designation CJ-4 or CK-4 for the diesel engine.
Failure to use the recommended oil can damage the
DPF and result in engine damage not covered by
the vehicle warranty.
Viscosity Grade
Use SAE 15W-40 viscosity grade engine oil. When it is
very cold, below 0°F (−18°C), use SAE 5W-40 to
improve cold starting. These numbers on the oil
container show its viscosity, or thickness.
5182573
The exhaust brake only activates when the
transmission torque converter is locked. This can vary
based on vehicle speed, gear, and load. To activate the
system, press the exhaust brake switch in the control
panel. A light in the switch will turn ON when the
exhaust brake is activated. The DIC displays the
message EXHAUST BRAKE ON for approximately
three seconds, then clears. To turn the brake OFF,
press the exhaust brake switch a second time. The DIC
displays the message EXHAUST BRAKE OFF for
approximately three seconds, then clears. The switch
must be pressed at each vehicle start for the system to
be active.
Exhaust Aftertreatment System
Tip: Depending on the Service Information being
referenced by the Technician, such as Diagnostic
Trouble Codes, Description and Operation, Component
Replacement Procedures, Power and Signal Master
Electrical Component List, Bulletins and the Electronic
Parts Catalog, component names for the various parts
in the Exhaust Aftertreatment System will vary.
Bulletin No.: 18-NA-366
November, 2019
Page 13
L5D Emission Control System Architecture
5138795
Legend
(1)
(2)
(3)
(4)
(5)
NOx Sensor 1 (B195A Nitrogen Oxides
Sensor 1)
EGT Sensor 2 (B131B Exhaust
Temperature Sensor 2)
Differential Pressure Sensor (B154
Diesel Particulate Filter Exhaust
Differential Pressure Sensor)
EGT Sensor 4 (B131D Exhaust
Temperature Sensor 4)
DEF Injector (Q61 Reductant Injector)
Exhaust Aftertreatment System
Diesel Fuel Requirements
Notice:
• Use Ultra Low Sulfur Diesel Fuel (ULSD) only.
Do Not use a diesel blend containing more than
20% biodiesel by volume.
• Do Not Use Non-Highway Fuel. Fuel labeled as
off road or non-highway is typically very high in
sulfur content and will damage the emission
control system. Non-highway fuel is not
intended for use in on-highway vehicles and
does not have the fuel properties needed by the
Duramax® Exhaust Aftertreatment System to
properly function.
(6)
(7)
(8)
(9)
(10)
EGT Sensor 5 (B131E Exhaust
Temperature Sensor 5)
NOx Sensor 2 (B195B Nitrogen Oxides
Sensor 2)
Particulate Matter Sensor (B136 Exhaust
Particulate Matter Sensor)
EGT Sensor 3 (B131C Exhaust
Temperature Sensor 3)
EGT Sensor 1 (B131A Exhaust
Temperature Sensor 1)
Overview
The diesel exhaust aftertreatment system is designed
to reduce the levels of hydrocarbons (HC), carbon
monoxide (CO), oxides of nitrogen (NOx), and
particulate matter remaining in the vehicle’s exhaust
gases. Reducing these pollutants to acceptable levels
is achieved through a 3 stage process as follows:
1. The close coupled Diesel Oxidation Catalyst
(DOC) stage
2. The Diesel Particulate Filter (DPF) stage
3. The Selective Catalyst Reduction (SCR) stage
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November, 2019
Component Function
The main components function as follows:
– The Close Coupled Diesel Oxidation Catalyst (DOC)
removes exhaust HC and CO through an oxidation
process.
– Particulate Matter (PM) consisting of extremely small
particles of carbon remaining after combustion are
removed from the exhaust gas by the porous barrier
in the Diesel Particulate Filter (DPF) which lets the
gases pass through and retains the particulates.
– Diesel Exhaust Fluid (DEF), is injected into the
exhaust gases prior to entering the SCR. Within the
SCR, NOx is converted to nitrogen (N2) and water
vapor (H2O) through a catalytic reduction fueled by
the injected DEF. The SCR is a single assembly
canister, consisting of two separate SCR bricks
which are separated by a small space in which EGT
Sensor 5 resides.
Close Coupled Diesel Oxidation
Catalyst (Oxidation Catalytic Converter)
Close Coupled Diesel Oxidation Catalyst (Oxidation
Catalytic Converter) Overview
The close coupled DOC functions much like the
catalytic converter used with gasoline fueled engines.
As with all catalytic converters, the DOC must be hot in
order to effectively convert the exhaust HC and CO into
CO2 and H2O. On cold starts, the exhaust gases are
not hot enough to create temperatures within the DOC
high enough to support full HC and CO conversion. The
temperature at which conversion starts to occur is
known as light-off. Proper DOC function requires the
use of ultra-low sulfur diesel (ULSD) fuel containing
less than 15 parts-per-million (ppm) sulfur. Levels
above 15 ppm will reduce catalyst efficiency and
eventually result in poor driveability and one or more
DTCs being set.
Bulletin No.: 18-NA-366
consisting of thousands of porous cells. Half of the cells
are open at the filter inlet but are capped at the filter
outlet. The other half of the cells are capped at the filter
inlet and open at the filter outlet. This forces the
particulate-laden exhaust gases through the porous
walls of the inlet cells into the adjacent outlet cells
trapping the particulate matter. The DPF is capable of
removing more than 90% of particulate matter, or soot
carried in the exhaust gases.
Differential Pressure Sensor (Diesel Particulate
Filter Exhaust Differential Pressure Sensor)
Operation
Pressure connections at the DPF inlet and outlet allow
the Differential Pressure Sensor (DPS) to measure the
pressure drop across the DPF. The pressure drop
increases as trapped soot collects in the cells of the
DPF during vehicle operation. The rate at which soot
collects varies with the power demands placed on the
engine. If left unchecked, the increasing backpressure
will eventually result in a driveability problem. There are
two sensing elements in the Differential Pressure
Sensor (DPS), one for the upstream side of the DPF,
and the other for the downstream side. Pressure from
each side of the DPF is applied to the bottom side of a
silicon diaphragm in each sensing element;
atmospheric pressure is applied to the top side of each
diaphragm. Relative pressure differences in each
sensing element is converted to a voltage (V1 & V2).
The difference in these voltages is sent to the ECM. As
the DPF becomes clogged, the pressure on the
upstream side increases because of back pressure due
to the restriction of the exhaust gas flow through
the DPF.
DOC Operation
In addition to reducing emissions, the DOC also
generates the exhaust heat needed by the SCR stage
to perform its function. Exhaust gas temperature
sensors are located upstream and downstream of the
DOC. By monitoring the temperature differential
between these two sensors, the ECM is able to confirm
DOC light-off. Light-off is confirmed by a DOC output
temperature that is greater than its input temperature.
In order to generate the high exhaust temperatures
needed for regeneration, the aftertreatment system
increases exhaust temperatures by injecting additional
diesel fuel into the post combustion process.
Diesel Particulate Filter (Exhaust Particulate Filter)
Regeneration
Over time, the soot trapped on the cell walls acts to
restrict exhaust flow through the DPF reducing engine
efficiency. This restriction in exhaust flow produces a
pressure drop across the DPF that increases as the
once porous cell walls become saturated with trapped
soot. The DPS monitors the pressure drop across the
DPF and provides the ECM with a voltage signal
proportional to soot buildup. Once soot buildup reaches
a specified limit (100%), as signaled by the increased
pressure drop across the DPF, the ECM commands a
regeneration event to burn-off the collected soot during
normal vehicle operation. Regeneration events
occurring during vehicle operation are known as normal
regenerations as they occur automatically and without
driver knowledge. In general, the vehicle will need to be
driven safely at a steady speed, preferably without
stopping for approximately 20–30 minutes for a full and
effective regeneration to complete.
Diesel Particulate Filter (Exhaust
Particulate Filter)
Selective Catalyst Reduction (Warm up
Nitrogen Oxides Catalytic Converter)
Diesel Particulate Filter (Exhaust Particulate Filter)
Overview
The DPF captures diesel exhaust gas particulates, also
known as soot, preventing their release into the
atmosphere. This is accomplished by forcing
particulate-laden exhaust through a filter substrate
Selective Catalyst Reduction (Warm up Nitrogen
Oxides Catalytic Converter)
While diesel engines are more fuel efficient and
produce less HC and CO than gasoline engines, they
generate higher levels of Nitrous Oxide (NOx). In order
Bulletin No.: 18-NA-366
November, 2019
to meet today’s tighter NOx limits, an SCR catalyst,
using the injected DEF, is used to convert NOx into N2
and H2O.
NOx Sensor (Nitrogen Oxides Sensor) Operation
The ECM uses two smart NOx sensors to control
exhaust NOx levels. The first NOx sensor is located in
the DOC inlet and monitors the engine out NOx. The
second NOx sensor is located in the exhaust tailpipe
downstream of the SCR and monitors NOx levels
exiting the aftertreatment system. The smart NOx
sensors communicate with the ECM over the serial
data line.
The smart NOx sensors consist of two components, the
NOx module and the NOx sensor element that are
serviced as a unit. The NOx sensors incorporate an
electric heater that is controlled by the NOx module to
quickly bring the sensors to operating temperature. As
moisture remaining in the exhaust pipe could interfere
with sensor operation, there is a delay turning on the
heaters until the exhaust temperature exceeds a
calibrated value. This allows any moisture remaining in
the exhaust pipe to boil off before it can effect NOx
sensor operation. Depending on engine temperature at
start up, the delay can be less than a minute or as long
as two minutes. Typically, NOx sensor 1 will reach
operating temperature faster than NOx sensor 2 as it’s
closer to the engine’s hot exhaust. At idle or low engine
speeds, NOx sensor 2 may require up to 5 minutes to
reach operating temperature. The sensors must be hot
before accurate exhaust NOx readings are available to
the ECM.
Diesel Exhaust Fluid (Reductant) Overview
Diesel Exhaust Fluid (DEF) is a mixture of carefully
blended aqueous urea solution of 32.5% high purity
urea (Pharmaceutical Grade Urea) and 67.5%
deionized water. Within the SCR, exhaust heat
converts the urea into ammonia (NH3) that reacts with
NOx to form nitrogen, CO2, and water vapor. Optimum
NOx reduction occurs at SCR temperatures of more
than 480°F (250°C). At lower temperatures, NH3 and
NOx may react to form Ammonium Nitrate (NH4NO3)
which can lead to temporary deactivation of the SCR
catalyst. To prevent this, the ECM will suspend DEF
injection when the exhaust temperature is less than a
calibrated minimum.
Exhaust Gas Temperature Sensor (Exhaust
Temperature Sensor)
The engine uses Exhaust Gas Temperature (EGT)
management to maintain the SCR catalyst within the
optimum NOx conversion temperature range of
390–750°F (200–400°C). The ECM monitors the EGT
sensors located upstream and within the SCR in order
to determine if the SCR catalyst is within the
temperature range where maximum NOx conversion
occurs.
Page 15
Particulate Matter Sensor (Exhaust
Particulate Matter Sensor)
Particulate Matter Sensor (Exhaust Particulate
Matter Sensor)
The PM sensor determines the amount of particulates
(soot) in the diesel exhaust gas exiting the tailpipe by
monitoring the collection efficiency of the DPF and this
also assists in emission diagnostics. The PM sensor is
similar to the heated oxygen sensor with a ceramic
element but also includes an individually calibrated
control unit. The PM sensor sensing element includes
two comb-shaped inter-digital electrodes, a heater and
a positive temperature coefficient (PTC) resistor for
temperature measurement.
Particulate Matter Sensor (Exhaust Particulate
Matter Sensor) Operation
The operation of the PM sensor is based on the
electrical conductivity characteristic of the soot. As the
exhaust gas flows over the sensing element, soot is
absorbed in the combs between the electrodes,
eventually creating a conductive path. When the path is
formed, it generates a current based on the voltage
being applied to the element. The measurement
process continues until a preset current value is
reached. To avoid misleading readings, the sensor
operates on a “regenerative” principle, which means
the soot is removed by heating up the element to burn
off the carbon, before the measurement phase begins.
The amount of regenerations is based on vehicle
strategy; when the amount of regeneration is reached,
the cumulative current readings are used to determine
the amount of soot concentration in the exhaust gas,
and thus the collection efficiency of the DPF.
The PM sensor is operated in 3 successive modes:
1. Standby mode after power-up to ensure protective
heating. On power-up, the control unit starts the
heating process to avoid condensation of liquids
on the sensing element. Presence of liquid can
cause thermal shock during the heating process,
resulting in damage to the ceramic element.
Regeneration is not initiated until the dew point
temperature has been exceeded.
2. Regeneration mode is conducted before each
measurement to ensure a soot free sensing
element. Before starting measurements, absorbed
soot is burned off the sensing element by heating it
up; this ensures each measurement starts off at
the same condition. Regeneration is conducted for
a pre-determined period of time based on soot
level.
3. Measurement mode is when soot is actively
collected on the sensing element. The sensor
heater is deactivated during measurement, so the
temperature on the element is equivalent to that of
the exhaust gas. Voltage is applied until a preset
12 micro-amp current threshold is achieved due to
increasing current as the soot builds up on the
element. The time from the end of the regeneration
to reach the threshold is used to calculate the
concentration of soot in the exhaust gas.
Page 16
November, 2019
Diesel Exhaust Fluid (Reductant)
System
Diesel Exhaust Fluid (Reductant) Overview
The DEF system consists of the following components
located at the DEF reservoir:
• An electrically-operated DEF pump.
• An integrated DEF level sensor and DEF
temperature sensor.
• A DEF control module.
• A DEF quality sensor.
• DEF system heaters.
The remaining DEF system component is an
electrically-controlled DEF injector which is external to
the reservoir.
The on-board reservoir holds approximately 7 gallons
(26 liters) of DEF. A pump within the reservoir supplies
pressurized DEF to the DEF injector located upstream
of the SCR. A DEF level sensor within the DEF
reservoir provides the DEF control module a signal
indicating DEF level. The DEF pressure sensor
provides the DEF control module with a voltage signal
proportional to the DEF pressure generated by the DEF
pump. The DEF control module varies the duty-cycle of
the pump voltage to maintain DEF pressure within a
calibrated range.
When the ignition is turned OFF, the DEF pump will run
in reverse for about 45 seconds in order to purge the
supply line of DEF. There is a one minute delay
between ignition OFF and the start of purge to allow the
exhaust system to cool in order to prevent hot exhaust
gas from being drawn into the DEF line. The ECM also
commands the DEF injector open during the purge
process. Purging prevents the DEF from freezing in the
pump or supply line to the DEF injector.
The ECM energizes the DEF injector to dispense a
precise amount of DEF upstream of the SCR in
response to changes in exhaust NOx levels. Feedback
from NOx sensor 1 and NOx sensor 2 allow the ECM to
accurately control the amount of DEF supplied to the
SCR. If more DEF is supplied to the SCR than is
needed for a given NOx level, the excess DEF results
in what is called ammonia slip where significant levels
of ammonia exit the SCR. Since the NOx sensors are
unable to differentiate between NOx and ammonia,
ammonia slip will cause NOx sensor 2 to detect higher
NOx levels than actually exist.
Bulletin No.: 18-NA-366
Cold Weather Operation
A 32.5% solution of urea with 67.5% deionized
water will begin to crystallize and freeze at 12°F
(−11°C). At this ratio, both the urea and water will
freeze at the same rate, ensuring that as it thaws, the
fluid does not become diluted, or over concentrated.
The freezing and thawing of DEF will not cause
degradation of the product. There are 2 DEF heaters in
the system. DEF Heater 1 is in the DEF reservoir and
DEF Heater 2 is in the supply line to the DEF injector.
The DEF control module monitors the DEF temperature
sensor located within the reservoir in order to determine
if the DEF temperature is below its freeze point. If the
module determines that the DEF may be frozen, it
energizes the DEF heaters. DEF pump operation is
disabled for a calibrated amount of time to allow the
heaters an adequate amount of time to thaw the frozen
DEF. Once the thaw time period expires, the module
energizes the DEF pump to circulate warm DEF back to
the reservoir to speed thawing. The ECM looks for an
increase in the DEF temperature to verify that the DEF
reservoir heater is working.
Diesel Exhaust Fluid Level Gauge
5182514
The DEF level must be maintained for the vehicle to
run properly. As the DEF level becomes low, warnings
are displayed on the DIC. These warnings will increase
in intensity as the DEF level is reduced. As the tank
nears empty, vehicle speed will be limited in a series of
steps. At least 2 gallons (7.57L) of DEF must be added
to release the engine speed limitation.
Bulletin No.: 18-NA-366
November, 2019
Recommended DEF — Storage and
Transfer — DEF Reservoir
Page 17
extended exposure to temperatures warmer than 75°F
(23.8°C), the ammonia scent grows stronger, indicating
nitrogen has vaporized, changing the urea-to-water
ratio of the product. Because DEF is highly reactive to
many metals, it must be stored in stainless steel,
polypropylene or high-density polyethylene (HDPE)
storage tanks. All pumps, valves and fittings must be
DEF compatible and used only to transfer DEF.
Recommended DEF
DEF Reservoir
5138259
API Certified Diesel Exhaust Fluid Mark
• GM DEF is an aldehyde free, NOx reducing
treatment. It is a mixture of 32.5% high purity
synthetic urea and 67.5% deionized water. GM
DEF meets the stringent ISO 22241 standard for
purity and concentration. GM DEF is a stable,
colorless, non-flammable, non-toxic primary
component used to help convert NOx, an
environmental pollutant, into harmless nitrogen
and water. Use Diesel Exhaust Fluid GM
PN 19286291 or DEF that meets the International
Organization for Standardization ISO 22241
specification or displays the API Certified Diesel
Exhaust Fluid Mark (meets API certification
requirements). Classified as minimum risk for
transportation.
• ACDelco® DEF is an aldehyde free, NOx reducing
treatment. It is a mixture of 32.5% high purity
synthetic urea and 67.5% deionized water.
ACDelco® DEF meets the stringent ISO 22241
standard for purity and concentration. ACDelco®
DEF is a stable, colorless, non-flammable,
non-toxic primary component used to help convert
NOx, an environmental pollutant, into harmless
nitrogen and water. It meets API regulations, and
meets or exceeds GM OE specifications.
Classified as minimum risk for transportation.
Storage and Transfer of DEF
DEF has a shelf life of approximately 24 months, but
when exposed to sunlight or prolonged exposure to
temperatures warmer than 75°F (23.8°C), the nitrogen
in DEF begins to volatilize into ammonia gas and can
reduce shelf life. Once volatilized, it will not go back into
suspension and the percentage of urea in the product
decreases to less than the optimum 32.5%. Fresh DEF
has a slightly pungent smell of ammonia. After
5124361
The DEF reservoir cap is blue and is positioned on the
right fender behind the front wheel for easy reservoir
fluid refills. It is recommended to fill the DEF tank on
level ground and when the engine is not running.
DEF Warning Light
5152580
When there is an issue with the DEF such as a low fluid
level or fluid contamination, the DEF Warning Light will
illuminate, a DIC message will display and a chime will
Page 18
November, 2019
sound. To avoid vehicle speed limitations, fill the DEF
tank at the first opportunity after a Low Fluid Level
warning message displays.
DEF Website
For more information, click on:
Regeneration
Bulletin No.: 18-NA-366
damaging high temperatures within the DPF. Vehicles
operated for short distances or extended idle where
normal regeneration does not occur will eventually
reach a high soot load condition. When the increased
pressure drop across the DPF is detected by the DPS,
the ECM illuminates the DPF lamp in the instrument
cluster and sends a Clean Exhaust Filter message to
the DIC.
Service Regeneration
Normal Regeneration
Over time, the soot trapped on the cell walls acts to
restrict exhaust flow through the DPF reducing its
effectiveness as well as reducing engine efficiency.
This restriction in exhaust flow produces a pressure
drop across the DPF that increases as the once porous
cell walls become saturated with trapped soot. A DPS
monitors the pressure drop across the DPF and
provides the ECM with a voltage signal proportional to
soot buildup. Once soot buildup reaches a specified
limit (100%), as signaled by the increased pressure
drop across the DPF, the ECM commands a
regeneration event to burn-off the collected soot during
normal vehicle operation. Regeneration events
occurring during vehicle operation are known as normal
regenerations as they occur automatically and without
driver knowledge. In general, the vehicle will need to be
driven safely at a steady speed, preferably without
stopping for approximately 20–30 minutes for a full and
effective regeneration to complete.
The frequency of normal DPF regeneration in this
system is determined by soot accumulation using the
pressure drop across the DPF and engine run time
which is approximately 18 hours. The L5D does not
utilize a Hydrocarbon (HC) Injector, so in order to
initiate a normal DPF regeneration event, the ECM
commands additional post injection diesel fuel in order
to create the additional exhaust heat in the DOC
necessary to promote regeneration and burn-off the
collected soot in the DPF.
During regeneration exhaust temperatures may exceed
1,184°F (640°C) due to the rapid catalytic combustion
of soot within the DPF. Conversely, under low engine
speed or light loads, exhaust temperatures may be too
low to promote proper regeneration. To protect the DPF
catalyst from thermal damage due to excessive soot
combustion, the ECM monitors the EGT sensors
upstream and downstream of the DPF during
regeneration. If the vehicle is slowed to idle speed
during a normal DPF regeneration, the engine may
maintain an elevated idle of 900 RPM until the DPF is
cooled to a calibrated temperature.
Should the EGT sensors indicate that regeneration
temperatures have exceeded a calibrated threshold,
regeneration will be temporally suspended until the
sensors return to a normal temperature. If regeneration
temperatures fall below a calibrated threshold,
regeneration is terminated and a corresponding DTC is
set in the ECM.
Under most conditions, the soot collected within the
DPF burns off during normal regeneration cycles.
Periodic regeneration prevents the buildup of soot from
reaching a level where its burn-off could produce
Exhaust temperatures at the tailpipe may exceed
572°F (300°C) during service regeneration. Observe
the following precautions:
• Service regeneration must be performed
outdoors. Most exhaust removal hoses cannot
withstand the high exhaust temperatures
generated during regeneration.
• Park the vehicle outdoors and keep people, other
vehicles, and combustible material away during
service regeneration.
• Park the vehicle in an area that provides a
clearance area of at least 10 feet on all sides of
the vehicle and open the hood.
• Ensure the tailpipe is not obstructed by mud or
debris.
• Do not leave the vehicle unattended during
service regeneration.
The ECM uses two EGT sensors to measure the
temperature of the exhaust gases at the inlet and outlet
of the DPF. Optimum DPF temperature is critical for
emission reduction and for ensuring complete
regeneration. Excessive DPF temperatures could
damage the ceramic substrate. The ECM monitors the
inlet and outlet EGT sensors in order to maintain the
DPF at its optimum temperature.
Service Regeneration Precautions
Warning: Tailpipe outlet exhaust temperature will
be greater than 572°F (300°C) during this
procedure. To help prevent personal injury or
property damage from fire or burns, perform the
following:
1. Do not connect any shop exhaust removal hoses
to the vehicle tailpipe.
2. Park the vehicle outdoors and keep people, other
vehicles, and combustible material away during
this procedure.
3. Do not leave the vehicle unattended.
Should the vehicle operator fail to drive the vehicle
within the conditions necessary to initiate a normal
regeneration cycle, the ECM illuminates the Service
Engine Soon lamp and displays a REDUCED ENGINE
POWER message on the DIC once the soot buildup
exceeds a calibrated value. The vehicle will remain in
the REDUCED ENGINE POWER mode until service
regeneration is performed.
Service regeneration is required because the amount of
soot collected in the DPF, known as soot load, is too
high to be burned off without possible thermal damage
to the DPF’s ceramic substrate. Service regeneration is
one of several output control functions available on the
Bulletin No.: 18-NA-366
November, 2019
scan tool. When service regeneration is commanded,
the ECM takes control of engine operation until the
service regeneration is completed in approximately
35 minutes or until the service regeneration is either
cancelled by the technician or is aborted by the ECM
when it detects unexpected conditions. The ECM
commands additional post injection diesel fuel in order
to create the additional exhaust heat in the DOC
necessary to promote regeneration and burn-off the
collected soot in the DPF. The service regeneration can
be terminated by applying the brake pedal,
commanding service regeneration OFF using the scan
tool, or disconnecting the scan tool from the vehicle.
(Q20 Intake Air Flow Valve)
The Intake Air Flow Valve is located upstream of the
intake air heater, and is normally in the open position.
The ECM commands the valve to close in order to
precisely control combustion temperature during DPF
regeneration. The IA valve will ensure the temperature
of the exhaust gas remains in an efficient range under
all operating conditions. The IA valve system uses a
position sensor located within the valve assembly to
monitor the position of the valve. The IA valve uses a
motor to move the valve to a closed position and spring
tension returns it to the open position. The motor is
operated through Motor Control 1 and Motor Control 2
circuits.
Ash Loading
Ash is a non-combustible by-product from normal oil
consumption. Low ash content engine oil (CJ-4 or
CK-4) is required for these vehicles with the exhaust
aftertreatment system. Ash accumulation will eventually
cause a restriction in the DPF. Being non-combustible,
ash is not burned off during regeneration. A DPF that is
ash loaded will need to be removed from the vehicle
and replaced.
Manual Regeneration
Page 19
may be under the Settings menu. If the vehicle cannot
be stopped when the DIC message first indicates
cleaning is available, automatic self-cleaning may have
begun. If conditions cannot be met for self-cleaning to
complete, and manual regeneration is selected, it may
take up to four minutes for the system to switch to
manual regeneration. When the switch occurs, a DIC
message prompts to start the cleaning process. After
making sure all of the safety conditions have been met,
press the trip odometer reset stem or the check-mark
symbol on the steering wheel control for at least one
second to select Start on the infotainment display.
Follow the instructions in the DIC messages. Touch
ACCEPT to acknowledge that all of these safety
conditions have been met and to activate regeneration.
Continue to follow the instructions in the DIC
messages. Hold the Exhaust Brake switch on the
instrument panel below the climate controls for more
than three seconds, and then release it, to begin the
regeneration process.
If the EXHAUST BRAKE ON message displays, then
the switch was released too soon. Press it again to turn
OFF the exhaust brake, then try again when the DIC
message prompts.
When manual regeneration begins, the engine speed
increases, the engine cooling fan sound increases, and
a DIC message indicates that cleaning is in progress.
A DIC message will display when cleaning has
completed. The message will remain as long as
cleaning is not necessary. Cleaning could take up to
30 minutes. Upon completion, the engine will return to
normal idle, but exhaust components will remain hot for
several minutes. Do not move the vehicle until the
exhaust has had time to cool. Manual regeneration can
be canceled at any time by pressing the brake pedal or
turning the engine off. Unusual noises may be heard if
regeneration is interrupted.
Exhaust Gas Recirculation
Manual Regeneration Overview
Important: This feature is available as an option.
To verify if the vehicle has this feature, refer to Build
Information in Investigate Vehicle History (IVH) or click
on: to contact the GM Upfitter Integration Group for
assistance.
If equipped, this feature allows for manual regeneration
of the DPF when it is unable to clean itself. It may be
necessary to perform a manual regeneration if driving
conditions, such as extended slow speed, stop-and-go
traffic, extended idle times, short drive cycles, or
stationary PTO operation, prevent DPF self-cleaning.
EGR Purpose
The Exhaust Gas Recirculation (EGR) system is used
to reduce the amount of nitrogen oxide (NOx) emission
levels caused by high combustion temperatures. At
temperatures above 1,371° C (2,500° F) oxygen and
nitrogen combine to form NOx. Introducing small
amounts of exhaust gas back into the combustion
chamber displaces the amount of oxygen entering the
engine. With less oxygen in the air/fuel mixture, the
combustion pressures are reduced, and as a result,
combustion temperatures are decreased, restricting the
formation of NOx.
Starting Manual Regeneration
Manual regeneration can only be used when the DPF
has become at least 90% full. At 100% full, it will
attempt to automatically self-clean if proper driving
conditions are met. The DPF will clean itself if the
vehicle can be driven more than 30 mph (50 km/h) for
about 30 minutes. A DIC message displays when
manual regeneration is possible. Scroll through the DIC
pages to find the Exhaust Cleaning menu. Depending
on whether the vehicle has a base or up-level cluster, it
EGR Operation
Air coming from the intake air filter housing is
compressed by the turbocharger, cooled by the charge
air cooler and mixed with cooled exhaust gas coming
from the exhaust gas recirculation EGR valve. The
exhaust gas mixes with the intake air to satisfy
emissions, performance, fuel economy and cool the
combustion process. The Mass Air Flow (MAF) sensor
signal is used by the ECM to detect the proper amount
of EGR flow. The ECM will close the EGR valve, then
Page 20
November, 2019
open the EGR valve to 100%. The ECM will then
calculate the MAF difference and determine if the
proper EGR flow has been detected. The recirculated
gas also prevents the formation of NOx related gases,
refer to as NOx emissions, which are a common cause
for failing emissions testing. When a failure occurs both
the air intake system and exhaust system should be
checked in order to isolate the root cause.
Marketplace, GM’s In-Vehicle
Commerce Platform
Tap, Tap and Away — Pay for Fuel Directly From
Your Dashboard
Through Marketplace, GM’s in-vehicle commerce
platform, drivers can pay for fuel through their
infotainment touchscreens at more than 22,000
different Shell, Exxon and Mobil stations across the
U.S. The process is simple. First, the owner needs to
download Marketplace from the vehicle’s app shop (on
the infotainment touchscreen) and link either an
ExxonMobil Speedpass+™ account or a Shell Fuel
Rewards® account. If they don’t have an existing
account, Marketplace will send an email to create a free
account and start collecting rewards points.
Once a rewards account is linked, the driver can pull
into the nearest eligible fuel station, select the pump
number and activate the fuel pump with a few simple
clicks on the infotainment touchscreen. The fuel cost is
charged to the payment method on file and drivers can
earn ExxonMobil Speedpass+™ or Shell Fuel
Rewards® points with each transaction. All of this can
be done without swiping a card or paying with cash,
providing security and convenience to GM vehicle
owners.
This technology requires no mobile phone and takes
fewer steps than other fuel payment features on the
market. The service is powered by Marketplace, the
automotive industry’s first commerce platform for
on-demand reservations and purchases of goods and
services.
Power Take-Off
Overview
If equipped, the Power Take-Off (PTO) is used to create
an auxiliary power source for running add-on
equipment, such as salt spreaders, snow plows,
winches, and lift buckets. The PTO system controls
engine speed to values higher than normal base idle,
PTO load relay engagement, and remote starting and
shutdown of the engine. When installing PTO
aftermarket equipment, the PTO wiring and operation
recommendations provided by the service manual and
GM Upfitter documentation must be followed.
Refer to the bulletins in the GM Upfitter Integration
Group website for the Power Take-Off operating
description and application guide. Click on:
Bulletin No.: 18-NA-366
Primary PTO Operating Modes
Refer to the Owner Manual for the Preset Enable
Conditions for each Mode before operating. PTO
modes of operation are:
• Preset: Stationary operation only: In-cab control
is standard, remote control is available.
Remote Operation requires programming with the
GM Service Tool and remote switch panel
provided by GM Upfitter Group.
• Variable: Stationary operation only: In-cab
control is standard, remote control is available.
Remote Operation requires programming with the
GM Service Tool and remote switch panel
provided by GM Upfitter Group.
• Mobile: In-cab control only.
This requires programming with the GM
Service Tool.
• Operator Selectable In-Cab Mode (OSIM):
OSIM is for in-cab operation only. OSIM is for
vehicles that require both stationary and mobile
modes.
OSIM is available via the GM Service Tool only.
During the configuration of OSIM, two modes must
be paired. The options for pairing are: stationary
preset and mobile, or stationary variable and
mobile.
Refrigerant R-1234yf
Air Conditioning Service Fittings
Service fittings meeting SAE J639 are used on these
vehicles for R-1234yf refrigerant. GM has chosen gray
caps to designate systems with R-1234yf.
A/C Compressor (Manual)
The A/C compressor uses a conventional belt driven
magnetic clutch to engage and mechanically turn the
compressor. When the A/C switch is pressed, the
HVAC control module sends an A/C request message
to the ECM via serial data. If specific criteria is met, the
ECM then grounds the A/C compressor clutch relay
control circuit, which will switch the A/C compressor
clutch relay. With the relay contacts closed, battery
voltage is supplied to the permanently grounded A/C
compressor clutch. The A/C compressor clutch will then
be activated.
This A/C system utilizes a variable displacement
solenoid valve to alter the amount of displacement
created by the turning of the compressor. The HVAC
control module provides both battery voltage and a
pulse width modulated ground to the variable
displacement solenoid valve. When the A/C switch is
pressed, the HVAC control module grounds the
variable displacement solenoid using a pulse width
modulation (PWM) signal in order to determine the
amount of compressor displacement. The performance
of the A/C compressor is regulated based on
cooling load.
Bulletin No.: 18-NA-366
November, 2019
A/C Evaporator Temperature Sensor
The evaporator temperature sensor is a 2-wire negative
temperature co-efficient thermistor. The sensor
operates within a temperature range of −40 to +185°F
(−40 to +85°C). The sensor is installed at the
evaporator and measures its temperature. If the
temperature drops below 38°F (3°C), the compressor
will be switched OFF in order to prevent evaporator
icing.
A/C Refrigerant Pressure Sensor
The A/C refrigerant pressure sensor is a 3-wire
piezoelectric pressure transducer. The sensor has a
5 V reference voltage, low reference, and signal circuit.
The A/C pressure signal can be between 0.2–4.8 V.
When the A/C refrigerant pressure is low, the signal
value is near 0 V. When the A/C refrigerant pressure is
high, the signal value is near 5 V. The ECM converts
the voltage signal to a pressure value. When pressure
is too high or too low, the ECM will not allow the A/C
compressor clutch to engage.
Actuators
Doors in the HVAC case assembly are used to control
air flow. The HVAC control module operates the doors
through the use of actuators, with one actuator being
used for each door. The system has the following air
control doors and associated actuators: mode,
temperature, and recirculation.
Blower Motor
The blower motor speed control signal from the HVAC
Control Module, battery positive and ground circuits
enable the blower motor to operate. The blower motor
control circuitry is integrated within the blower motor
assembly. The HVAC control module provides a low
side PWM signal to the blower motor to request a
specific motor speed. The blower motor translates the
PWM signal and drives the motor accordingly.
Rear Vision Camera
Important: The RVC camera is shipped loose in the
cab for upfitter installation.
If equipped, the Rear Vision Camera (RVC) may help
the driver park or avoid objects. Always check around
the vehicle when parking or backing. When the vehicle
is shifted into R (Reverse), the RVC displays an image
of the area behind the vehicle in the infotainment
display. The previous screen displays when the vehicle
is shifted out of R after a short delay. To return to the
previous screen sooner, press any button on the
infotainment system, shift into P, or reach a vehicle
speed of approximately 8 mph (12 km/h).
Refer to the GM Upfitter Integration Group website for
mounting locations.
Refueling the Vehicle
The fuel fill port(s) is located on the driver side of the
vehicle. If equipped with dual fuel tanks, each tank
must be filled through its own fill port.
Page 21
Supplemental Inflatable Restraint
System
SIR System Overview
The Supplemental Inflatable Restraint (SIR) system
supplements the protection offered by the seat belts.
The SIR system contains an inflatable restraint sensing
and diagnostic module (SDM), the airbags, seat belt
pretensioners (retractor), and impact sensor. When the
SDM detects a collision, it will process the information
provided by the sensors to further support airbag or
pretensioner deployment. The SDM will deploy the
airbags and pretensioners if it detects a collision of
sufficient force. If the force of the impact is not sufficient
to warrant airbag deployment, the SDM may still deploy
the seat belt pretensioners. The SDM contains a
sensing device that converts vehicle velocity changes
to an electrical signal. The SDM compares these
signals to values stored in memory. If the signals
exceed a stored value, the SDM will determine the
severity of the impact and either cause current to flow
through the frontal deployment loops deploying the
frontal airbags and pretensioners, or it will deploy the
pretensioners only. The SDM continuously monitors the
deployment loops for malfunctions and illuminates the
AIRBAG indicator if a fault is detected. The SDM
performs continuous diagnostic monitoring of the SIR
system electrical components. Upon detection of a
circuit malfunction, the SDM will set a DTC and inform
the driver by illuminating the AIRBAG indicator. The
steering column and knee bolsters are designed to
absorb energy and compress during frontal collisions in
order to limit leg movement and decrease the chance of
injury to the driver and passenger.
Inflatable Restraint Sensing and Diagnostic Module
The SDM is a microprocessor and the control center for
the SIR system. The SDM contains internal sensors
along with an external impact sensor mounted at a
strategic location on the front of the vehicle. In the
event of a collision, the SDM compares the signals from
the internal and external impact sensors to a value
stored in memory. When the generated signals exceed
the stored value, the SDM will cause current to flow
through the appropriate deployment loops to deploy the
airbags. The SDM records the SIR system status when
a deployment occurs and illuminates the AIRBAG
indicator located in the instrument cluster.
Airbags
This vehicle contains 2 airbags. The 2 airbags are
located in the steering wheel (single inflator) and
instrument panel on the passenger side (single inflator).
Airbags contain a housing, inflatable airbag, initiating
device, canister of gas generating material and in some
cases, stored compressed gas. The deployment loops
supply current through the inflator modules to deploy
the airbags. For moderate frontal collisions the airbags
deploy at less than full deployment which consists of
stage 1. The current passing through the airbag, ignites
the material in the canister producing a rapid
generation of gas and is some cases, the release of
compressed gas. The gas produced from this reaction
rapidly inflates the airbag. Once the airbag is inflated it
Page 22
November, 2019
quickly deflates through the airbag vent holes and/or
the airbag fabric. Each airbag is equipped with a
shorting bar located in the connectors of the module.
The shorting bar shorts the airbag deployment loop
circuitry to prevent unwanted deployment of the airbag
when it is disconnected.
Impact Sensor
There is one impact sensor which is located in the front
of the vehicle. The impact sensor contains a sensing
device which monitors vehicle acceleration to detect
collisions that are severe enough to warrant airbag
deployment. The impact sensor is not part of the
deployment loop, but instead provides input to the
SDM. The SDM contains a microprocessor that
performs calculations using the measured inputs from
acceleration and pressure sensors. When the
generated calculations exceed the stored value, the
SDM will cause current to flow through the deployment
loops deploying the appropriate airbags.
Seat Belt Pretensioners
Important: Once a pyrotechnic pretensioner is
activated it must be replaced.
The pyrotechnic pretensioner is the most sophisticated
type of pretensioning device. The seat belt
pretensioners for the driver and passenger consist of a
housing, the seat belt retractor which is located in the
B-pillar, seat belt webbing, an initiator and a canister of
gas generating materials. The initiator is part of the seat
belt pretensioner deployment loop. When the vehicle is
involved in a collision of sufficient force, the SDM
causes current to flow through the seat belt deployment
loops to the initiator. Current passing through the
initiator ignites the material in the canister producing a
rapid generation of gas. The gas produced from this
reaction deploys the seat belt pretensioners which
removes all of the slack in the seat belts. Depending on
the severity of the collision, the seat belt pretensioners
may deploy without the frontal airbags deploying, or
they will deploy immediately before the frontal airbags
deploy. Each seat belt pretensioner is equipped with a
shorting bar that is located in the connector of the seat
belt pretensioner. The shorting bar shorts the seat belt
pretensioner circuitry to prevent unwanted deployment
of the seat belt pretensioner when the connector is
disconnected.
Snow Plow
If a snow plow is added to the vehicle, the airbags
should still work properly. The airbag systems were
designed to work properly under a wide range of
conditions, including snow plowing with vehicles that
have the optional snow plow prep package —
RPO VYU
Do not change or defeat the snow plow's "tripping
mechanism." If you do, it can damage the snow plow
and the vehicle, and may cause an airbag deployment.
Bulletin No.: 18-NA-366
Suspension — Air Ride
Operation
If equipped, the Air Ride Suspension provides a
smooth, shock and vibration free ride with a preset
constant frame height. The air springs on the air ride
suspension take the place of steel springs, which
eliminates the need to overcome inter-leaf friction
resulting in a minimum amount of road shock being
transferred to the frame, cargo and suspension. The air
ride suspension adjusts to load changes automatically,
providing a low rate suspension with a light or no load
condition, and a higher rate suspension with heavier
loads.
Air Ride Suspension Dump Switch
5124391
Control button positioning may vary depending on
equipment and options.
The air ride suspension system allows the rear
suspension to be temporarily lowered by approximately
6 inches. The system is controlled by the Air
Suspension Dump (ASD) switch in the center stack.
This switch controls solenoids, which direct air to the
suspension dump and height valve. Pressing the ASD
switch when the vehicle is in P and the ignition is in the
ON/RUN position releases air supplied to the rear
suspension, lowering (dumping) the rear air suspension
for loading. The indicator on the ASD switch
illuminates. When the vehicle is shifted out of P, air is
filled into the system and the indicator on the switch will
turn OFF. Vehicles with air suspension have an AUX
warning lamp immediately to the left of the ASD switch.
The suspension may refill slowly if this lamp is ON.
Suspension — Front
Non-Driving Axle
The non-driving axle is a solid I-Beam type with
knuckles attached by kingpins. By matching steering
geometry with specific wheelbase lengths, tire scrub
and premature tire wear are reduced.
Bulletin No.: 18-NA-366
November, 2019
The front axle has two primary functions:
– Support the front of the truck including the load.
– Provide good maneuverability through steering
control.
Page 23
Tire/Certification Label Legend
Leaf Springs
Tapered leaf springs are used at the front axle.
Parabolic tapered leaf springs are thicker in the middle
than at the ends. Because of this design, these
suspensions are able to use fewer spring leaves, which
helps to reduce leaf-to-leaf friction and produces a
smoother ride than flat multi-leaf springs.
Stabilizer Bar
The stabilizer bar reduces body roll while turning,
keeping weight more evenly distributed above all
wheels, improving traction and reducing tire wear.
Suspension — Rear
Multileaf Variable Rate Springs
This leaf spring design offers a variable deflection rate
by changing the effective length of the spring with the
use of a cam-type frame mounting bracket. As the
spring deflects, due to increased load, the point of
spring contact on the bracket moves toward the center
of the spring, making it stiffer as the load increases.
This type of rear suspension provides good stability
and control.
Tires and Wheels
Tire/Certification Label
The Tire/Certification Label is typically located on the
driver side door frame of the vehicle and indicates the
size of the original equipment tires installed on each
axle of the vehicle. The load rating of the tires installed
on the vehicle at the time of production is at or in
excess of the Gross Axle Weight Rating (GAWR) on the
Tire/Certification Label. When replacing the tires be
sure the replacement tire load rating (listed separately
in pounds and kilograms on the tire sidewall for single
or dual applications) multiplied by the number of tires
on that axle is equal to or higher than the specified
listed Steer Axle or Drive Axle GAWR. Failure to do so
will adversely affect maximum load-carrying capacity.
Tires with the same size specifications do not always
have the same load specification. Dual tires should be
matched using tires of equivalent size. Tires which
differ more than 1/4 in (6 mm) in diameter or 3/4 in
(19 mm) in circumference should not be mounted on
the same dual wheel assembly.
5152209
1.
2.
3.
4.
Gross Weight Rating of the Front Axle
Tire Size for Front Axle
Tire Size for Rear Axle
Gross Weight Rating of the Rear Axle
Tires — Lug and Rib Patterns
While a truck’s application plays the primary role in
selecting a tire tread pattern, there are really only two
options, lug and rib. Lug patterns can be closed or open
shoulder design, and are typically used on drive axles.
Rib patterns can be straight or zigzagged and typically
are used on steer and trailer axles. A straight rib pattern
is designed for high mileage, good fuel economy and
resistance to irregular wear. The zigzagged pattern
offers additional biting edges for improved traction on
wet road surfaces. Use tires of the same type on the
same axle.
Tires
The vehicle can be equipped with the following:
– Tires: Front, 225/70R19.5G Highway, Blackwall,
Continental (Standard)
– Tires: Rear, 225/70R19.5G Highway, Blackwall,
Continental (Standard)
– Tires: Front, 225/70R19.5G Highway, Blackwall,
Goodyear (Available)
– Tires: Rear, 225/70R19.5G Highway, Blackwall,
Goodyear (Available)
– Tires: Rear, 225/70R19.5G Traction, Blackwall,
Continental (Available)
– Tires: Rear, 225/70R19.5G Traction, Blackwall,
Goodyear (Available)
– Tire: Spare, Match Tire to Vehicle Equipment
Tire Rotation
Tires should be rotated every 7,500 mi (12,000 km).
Tires are rotated to achieve a uniform wear for all tires.
The first rotation is the most important. The outer tire on
a dual wheel setup generally wears faster than the
inner tire. Adjust the front and rear tires to the
Page 24
November, 2019
recommended inflation pressure on the Tire and
Loading Information label after the tires have been
rotated.
Bulletin No.: 18-NA-366
Wheels — Overview
While some steel wheels look similar and some
aluminum alloy wheels look very similar, there is more
of a difference in them than can normally be seen by
the naked eye, when they are already mounted on a
vehicle. The two basic types of commercial wheels are
determined by how the wheel is centered on the hub.
Stud Piloted wheels have tapered stud holes and the
lug nuts have a matching taper. The centering of each
lug nut in the stud hole of the wheel will cause the
wheel to be centered on the hub. The hub hole in the
wheel only serves to allow hub clearance. Hub Piloted
wheels use the center hole of the wheel (hub bore) to fit
over the matching size ridge on the hub. The wheel is
centered on the hub by the hub bore. The lug nuts will
have a flush face in contact with the wheel. The lug
nuts only secure the wheel to the hub. Interchanging
lug nuts between the two different style of wheels is
NOT recommended and could cause damage to the
wheel or more. To avoid surface damage on wheels
and wheel trim, do not use strong soaps, chemicals,
abrasive polishes, cleaners, or brushes. Use only GM
approved cleaners. Do not drive the vehicle through an
automatic car wash that uses silicone carbide tire/
wheel cleaning brushes.
Tire Rotation Pattern — Aluminum Wheels
5152010
Vehicles with aluminum wheels have two unique
wheels. They are aluminum front and rear outer
wheels, and steel rear inner wheels. The aluminum
wheels can only be rotated using the front and rear
outer positions. The steel wheels can only be rotated
on the rear inner positions. Use this rotation pattern
when rotating tires that are mounted on aluminum
wheels.
Tire Rotation Pattern — Steel Wheels
Wheel Size — Material — Color
Notice: On a vehicle that is equipped with
aluminum wheels, the two front and two outside
rear wheels are aluminum. The two rear inner
wheels are steel.
The wheel selections are:
– Wheels: 19.5" x 6.75", Steel, Black Painted,
8-holes, Hub Piloted (Standard)
– Wheels: 19.5" x 6.75", Steel, Grey Painted, 8-holes,
Hub Piloted (Available)
– Wheels: 19.5" x 6.75", Steel, White Painted,
8-holes, Hub Piloted (Available)
– Wheels: 19.5" x 6.75", Aluminum, 8-holes, Hub
Piloted (Available)
– Wheel: 19.5" x 6.75", Spare, Steel, Black, 8-holes,
Temporarily Mounted on Frame, Hub Piloted
(Available)
Traction Control System
5151982
Use this rotation pattern when rotating tires that are
mounted on steel wheels. DO NOT use this rotation
pattern for tires mounted on aluminum wheels.
If equipped, the steel spare wheel can be used in any
position in the event of a flat tire.
System Operation
The vehicle has a Traction Control System (TCS). This
system helps limit wheel spin and assist the driver in
maintaining control, especially on slippery road
conditions. TCS activates if it senses any of the drive
wheels are spinning or beginning to lose traction. When
this happens, TCS applies the brakes to the spinning
wheel(s) and reduces engine power to assist in limiting
wheel spin.
If the cruise control is being used and traction control
begins to limit wheel spin, the cruise control will
disengage. Cruise control may be turned back ON
when road conditions allow. The TCS turns ON
automatically when the vehicle is started and begins to
move. The system may be heard or felt while operating
or while it is performing diagnostic checks. This is
Bulletin No.: 18-NA-366
November, 2019
Page 25
normal and does not mean there is a problem with the
vehicle. It is recommended to leave TCS ON for normal
driving conditions, but it may be necessary to turn TCS
OFF if the vehicle gets stuck in sand, mud, ice, or snow.
Emergency Vehicle Series™
Allison Emergency Vehicle Series™ offers a complete
family of automatic transmissions to meet the special
needs of fire and emergency vehicles.
Turning the System OFF and ON
Highway Series™
Allison Highway Series™ automatic transmission are
designed to meet all the horsepower needs of strictly
on-highway vehicles that do not require a PTO
operation.
Motorhome Series™
Allison Motorhome Series™ automatic transmissions
are designed to provide enhanced performance and
exceptional value to the motorhome market.
Rugged Duty Series™
Allison Rugged Duty Series™ automatic transmissions
are suited for any vehicle that operates on/off highway
and requires PTO operation.
5181620
The control button for the TCS (shown) is on the center
stack control panel.
• To turn TCS OFF, press and release the button.
The Traction OFF light displays in the instrument
cluster. The appropriate message will display in
the DIC.
• To turn TCS ON, press and release the button.
The Traction OFF light displayed in the instrument
cluster will turn OFF.
Transmission Allison® 6-Speed
Notice: The Allison® Transmission and TCM will
be warrantied by Allison® and will have to be taken
to an Allison® Authorized Distributor and Dealer
Location for repair or replacement.
Transmission Component and System Description
The Allison® 6-speed fully automatic transmission
delivers solid fuel efficiency, superior performance and
outstanding vehicle safety. If equipped, Allison’s Power
Take-Off (PTO) provision, which draws energy from the
truck’s running engine, enables the operator to power
attachments and accessories with ease.
Depending on the vehicle, the following transmissions
are used on the 2WD and 4WD applications:
– Allison® 1700 with double overdrive
– Allison® 1750 with double overdrive
– Allison® 2700 with double overdrive
For additional transmission application information,
refer to the section titled: Gross Combined Weight
Rating Table
Automatic Transmission Shift Lock Control
The Automatic Transmission Shift Lock Control System
is a safety device that prevents an inadvertent shift out
of P when the engine is running. The driver must press
the brake pedal before moving the shift lever out of the
P position. The shift lock control solenoid is
permanently grounded. The BCM supplies voltage to
the automatic transmission shift lock control solenoid,
releasing the mechanical lock on the shift lever as the
solenoid energizes. The energized solenoid allows the
driver to move the shift lever out of the P position.
When the brake pedal is not applied, the BCM turns the
control voltage output of the shift lock control solenoid
OFF, de-energizing the shift lock control solenoid.
When the transmission is in P, the de-energized shift
lock control solenoid will prevent shifting as the lever is
mechanically locked in P.
The system consists of the following components:
– The Automatic Transmission Shift Lock Solenoid
(serviced as the Automatic Transmission Shift Lock
Actuator)
– The ECM
– The Body Control Module (BCM)
Transfer Case — Four-Wheel Drive
When equipped with four-wheel drive, the engine's
driving power can be sent to all four wheels for extra
traction.
Page 26
November, 2019
Manual Locking Hubs
Bulletin No.: 18-NA-366
Electronic Transfer Case Switch
5141552
5141562
The locking hubs are on each end of the front axle and
must be manually turned to LOCK before the
four-wheel drive modes can be used. The hubs may
remain in the LOCK position when road surface traction
conditions are variable or it is temporarily unsafe to exit
the vehicle and unlock them. When four-wheel drive is
no longer needed, turn the locking hubs to FREE. If the
hubs are locked when in two-wheel drive, driveline
vibration may be experienced.
Caution: Shifting the transmission into gear before
the requested mode indicator light has stopped
flashing could damage the transfer case.
All of the lights on the transfer case switch will flash ON
then OFF momentarily when the ignition is turned ON.
The light that remains ON indicates the current state of
the transfer case. The indicator mark on the switch
must line up with the indicator light before a shift can be
commanded. With the ignition ON, rotate the switch
located to the left of the steering wheel, to shift into and
out of four-wheel drive for extra traction. The light will
flash indicating that the shift is in progress. When the
shift is completed the new position will be illuminated. If
the transfer case cannot complete a shift command, it
will go back to its last chosen setting.
Bulletin No.: 18-NA-366
November, 2019
Page 27
Turbocharger System Description
Variable Vane Turbocharger Overview
4584300
Legend
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
Turbine Housing
Lower Vane Ring
Vane Ring Assembly Spacer
Upper Vane Ring Assembly
Adjusting Ring Assembly
V-Band Nut
V-Band
Compressor Housing Bolt
The turbocharger increases engine power by pumping
compressed air into the combustion chambers, allowing
a greater quantity of fuel to combust at the optimal air/
fuel ratio. The turbine spins as exhaust gas flows out of
the engine and over the turbine blades, and turns the
compressor wheel at the other end of the turbine shaft,
pumping more air into the intake system. This is a
BorgWarner single stage, water cooled, variable
geometry turbocharger (VGT) capable of producing
220 kPa (31.9 psi) boost pressure.
The ECM communicates with the turbocharger vane
position actuator via the controller area network (CAN)
bus to control the turbocharger vanes. The smart
actuator incorporates a brushless motor and is
mounted on top of the turbocharger. It is connected to
(9)
(10)
(11)
(12)
(13)
(14)
(15)
Core Assembly
Linkage Assembly
Linkage Assembly Nut
Compressor Housing O-Ring
Actuator Nut
Compressor Housing
Actuator
the vanes by a linkage rod. The vanes are used to vary
the amount of boost pressure and can control the boost
pressure independent of engine speed. The vanes
mount to a unison ring which is rotated to change the
vane angle. The ECM will vary the vane angle which
adjusts the boost dependent upon the load
requirements of the engine.
When the actuator arm is in the vertical top rest position
the turbocharger vanes are fully open. When the
actuator arm is in the horizontal bottom of travel
position the turbocharger vanes are fully closed.
The turbocharger vanes are normally open when the
engine is not under load. However, the ECM will often
close the turbocharger vanes to create back pressure
to drive exhaust gas through the Exhaust Gas
Page 28
November, 2019
Recirculation (EGR) valve as required. At extreme cold
temperatures, the ECM may close the vanes at low
load conditions in order to accelerate engine coolant
heating.
The turbocharger is also utilized as a component of the
exhaust brake system. Under certain conditions, the
ECM will automatically close the turbocharger vanes to
build back pressure in the exhaust, which reduces
engine speed and slows the vehicle without applying
the brakes.
During regeneration, the ECM will vary the
turbocharger vanes to assist with the exhaust system
warm-up, and to maintain proper engine exhaust
temperatures needed to properly regenerate the Diesel
Exhaust Particulate Filter (DPF).
Each time the ignition is turned OFF, the turbocharger
vane position actuator performs a learn procedure. The
actuator arm sweeps the turbocharger vanes from fully
open to fully closed to obtain a count value. This value
is compared to the previous value to ensure proper
vane position. Following the learn sweep the actuator
sweeps the vanes two more times to clean off
combustion soot.
Bulletin No.: 18-NA-366
3. Select the desired feature and setting. Settings are
saved automatically.
4. . Select BACK to exit each menu.
Bluetooth®
The Bluetooth® system allows users with a Bluetooth®
enabled cell phone to make and receive hands-free
calls using the vehicle audio system and controls.
Before using a Bluetooth® enabled device in the
vehicle, it must be paired with the in-vehicle Bluetooth®
system. The pairing process is disabled when the
vehicle is moving. When using the Bluetooth system,
sound comes through the vehicle's front audio system
speakers and overrides the audio system. Use the
volume control knob during a call to change the volume
level. The system maintains a minimum volume level.
Not all devices will support all functions.
Accessory Power Outlets — 110 Volt Power Outlet
— USB Ports
Depending on the type of seat
Vehicle Hoisting/Lifting
The Service Department will need a 25,000 pound
Hoist/Lift to raise the vehicle. For safety reasons, DO
NOT use jackstands or floor jacks.
Vehicle Personalization
5186598
•
5186413
Some vehicle features can be customized using the
Settings menus on the infotainment system. The
Settings menus may include Time and Date, Language,
Radio, Vehicle, Bluetooth, Apple CarPlay, Android
Auto, Voice, Display, Return to Factory Settings,
Software Information, Wi-Fi, and more.
1. Select Settings on the Home page.
2. Select the desired menu item.
Vehicles with bench seats have an accessory
power outlet and 110 volt power outlet that are
located on the lower-center of the instrument
panel. USB ports and an accessory power outlet
are located in the center seat storage
compartment.
Bulletin No.: 18-NA-366
November, 2019
Page 29
Gross Combined Weight Rating
Note: It is important to remember that the GCWR is
not an actual measurement of the weight of a tow
vehicle and a trailer, but rather the combined
maximum weight limit that the manufacturer has set
for the two vehicles once attached.
5186733
•
Vehicles with bucket seats have USB ports,
accessory power outlets and a 110 volt power
outlet that are located on the center console. USB
ports and an accessory power outlet also are
located in the center console storage
compartment.
Vehicle Label — Incomplete
A vehicle-specific Incomplete Vehicle Label is attached
to the driver-side door frame. The upfitter will add an
additional Label upon completion of the work to the
vehicle, directly above the Incomplete Vehicle Label.
Curb Weight
Curb Weight is the weight of a vehicle without the
driver, passengers or cargo but including the maximum
capacity of fuel, oil, coolant and other items of standard
equipment.
Gross Axle Weight Rating
Note: It is important to remember that a vehicle's
GAWR is not a measurement of how much weight
each axle is actually carrying at any given time. The
actual amount of weight each axle is carrying is the
gross axle weight or GAW.
A vehicle's GAWR is the specific weight determined by
the manufacturer to be the maximum allowable weight
that can be placed on an individual axle. Front and rear
axles have individual gross axle weight ratings. The
GAWR is a weight limit for each of the vehicle's axles
which is determined by the manufacturer. A vehicle's
axles should never be loaded beyond the
manufacturer's listed GAWR. The GAWR includes the
weight of the vehicle, passengers, cargo and trailer
tongue weight (if equipped). Of course, all of this weight
is distributed between two axles.
A specific vehicle’s GCWR is based on parameters
established by chassis manufacturers. The
manufacturer makes an assessment in accordance
with SAE International test protocols, determining
maximum GCWR. Additionally, the OEM runs stringent
tests based on internal requirements which may include
testing total GCWR braking capability using only the
towing vehicle chassis braking system. GCWR is the
total weight of the truck pulling the trailer and the trailer
itself. The truck chassis dictates proper GCWR for safe
operation of the combination truck and trailer. GCWR is
the total allowable weight of the completely loaded
vehicle and trailer including fuel, passengers, cargo,
equipment, and accessories. Do not exceed the GCWR
for the vehicle.
• 4500HD Regular/Crew Cab: GCWR 26,000–
30,000 lbs.
• 5500HD Regular/Crew Cab: GCWR 26,000–
30,000 lbs.
• 6500HD Regular/Crew Cab: GCWR 26,000–
30,000 lbs.
Gross Combined Weight Rating — Calculating
To check that the weight of the vehicle and trailer are
within the GCWR for the vehicle, follow these steps:
• Start with the "curb weight" from the trailering
information label.
• Add the weight of the trailer loaded with cargo and
ready for the trip.
• Add the weight of all passengers.
• Add the weight of all cargo in the vehicle.
• Add the weight of hitch hardware such as a draw
bar, ball, load equalizer bars and sway bars.
• Add the weight of any accessories or aftermarket
equipment added to the vehicle.
The resulting weight cannot exceed the GCWR of the
vehicle.
The gross combined weight can also be confirmed by
weighing the truck and trailer on a public scale. The
truck and trailer should be loaded for the trip with
passengers and cargo.
Gross Vehicle Weight Rating
Note: It is important to remember that the GVWR is
not a measurement of how much a vehicle actually
weighs. A vehicle's actual weight is the gross
vehicle weight, or GVW.
A truck’s GVWR is the maximum weight rating
established by the chassis manufacturer. The OEM will
determine the GVWR based on test results and vehicle
dynamic performance to ensure a safe, reliable truck.
Safety standards that apply to braking, vehicle stability,
and chassis manufacturer internal standards for
durability, dynamic stability and handling can restrict
GVWR to less than the sum of the gross axle weight
ratings (GAWR) for that vehicle. The GVWR is
Page 30
November, 2019
Bulletin No.: 18-NA-366
calculated by adding the vehicle’s listed curb weight,
the weight of any optional accessories, cargo, the
trailer tongue weight (if equipped) and passengers.
• 4500HD Regular/Crew Cab: GVWR 15,000–
16,500 lbs.
• 5500HD Regular/Crew Cab: GVWR 17,500–
19,500 lbs.
• 6500HD Regular/Crew Cab: GVWR 21,000–
22,900 lbs.
Gross Vehicle Weight
Gross Vehicle Weight (GVW) is the total weight of the
truck and payload at a point in time and will vary. The
GVW includes the vehicle’s listed curb weight, cargo,
equipment, trailer tongue weight (if equipped) and
passengers. Vehicle options, passengers, cargo, and
equipment reduce the maximum allowable tongue
weight the vehicle can carry, which also reduces the
maximum allowable trailer weight.
Gross Combined Weight Rating Table
Use this table to determine the Gross Combined
Weight Rating (GCWR) based on the model and
equipment.
Transmission
Axle Ratio
Maximum Trailer
Weight (2)
GCWR*
4500/5500/
6500HD 2WD
Allison® 1700
4:10/4:30/4:56/4.88
(1)
26,000 lbs (11,818 kg)
4500/5500/
6500HD 2WD
Allison® 1750
4:10/4:30/4:56/4.88
(1)
30,000 lbs (16,636 kg)
6500HD 2WD
Allison® 2700
4:10/4:30/4:56/4.88
(1)
26,000 lbs (11,818 kg)
4500/5500/
6500HD 4WD
Allison® 1700
4:30
(1)
26,000 lbs (11,818 kg)
4500/5500/
6500HD 4WD
Allison® 1750
4:30
(1)
30,000 lbs (16,636 kg)
6500HD 4WD
Allison® 2700
4:30
(1)
26,000 lbs (11,818 kg)
Vehicle
*The GCWR is the total allowable weight of the completely loaded vehicle and trailer including passengers, cargo equipment and
conversions. The GCWR for the vehicle must not be exceeded.
(1) Maximum Trailer Weight cannot be provided because total vehicle weight is unknown.
(2) Choose an appropriate hitch and load the truck and trailer within the limits of GCWR, GVWR, and GAWR (of the Rear Axle).
Integrated Trailer Brake Control
The Integrated Trailer Brake Control (ITBC) system can
be used to adjust the amount of power output, or Trailer
Gain, available to the trailer brakes. The control panel
is located on the left side of the instrument panel. ITBC
information is displayed on the DIC.
Bulletin No.: 18-NA-366
November, 2019
Page 31
GM Upfitter Integration Group
Operation
Important: When adding non OE content to a
vehicle, contact the GM Upfitter Integration Group
for assistance if needed.
1. Click on: to visit the GM Upfitter Integration Group
Home Page. Scroll to the bottom of the page and
click on: Contact Us / Request Data
2. A request form will appear in a new window. To
request technical assistance from the GM Upfitter
Integration Group, complete and submit the form.
Warranty Coverage at a Glance
•
•
5182686
•
To operate the system:
• Squeeze the levers together on the control panel
(the left lever does not move) to manually apply
the trailer brakes.
• Adjust the Trailer Gain by pressing the +/–
adjustment buttons on the control panel.
Roadside Assistance
Overview
Owners of the new 2019 Chevrolet Silverado Chassis
Cab Medium Duty vehicles are automatically enrolled in
the Chevrolet Roadside Assistance program for up to
5 years/100,000 miles, whichever occurs first, at no
expense to you. Chevrolet’s Roadside Assistance
toll-free number is staffed by a team of trained advisors
who are available 24 hours a day, 365 days a year, to
contact a service provider for light services such as fuel
delivery, jump-starts, flat tire and lock-outs or to make
arrangements to have the vehicle towed to the nearest
Chevrolet Dealer for any repairs. Services are provided
for the duration of the vehicle’s powertrain warranty. For
U.S.-purchased vehicles, call 1-888-899-1327.
(Text Telephone (TTY): 1-888-889-2438).
OnStar® Roadside Assistance
If you have a current OnStar® Safety & Security plan,
push the blue OnStar® button or red Emergency button
to get the help you need. An OnStar® advisor will use
GPS technology to pinpoint the vehicle location and
contact the nearest service provider. To learn more
about OnStar® services, push the blue OnStar® button
or click on: or call 1-888-4-ONSTAR (1-888-466-7827).
•
•
Bumper-to-Bumper: (Includes Tires) Coverage
is for the first 3 years or 36,000 miles, whichever
comes first.
Powertrain: 6.6 Duramax® Turbo-Diesel Engine
coverage is provided for 5 years or 100,000 miles,
whichever comes first.
Powertrain: The General Motors Powertrain
warranty on the Silverado chassis-cab 4500HD,
5500HD and 6500HD trucks excludes the
Allison® transmission and Transmission Control
Module (TCM). Investigate Vehicle History (IVH)
will display this as: Powertrain Ltd. Wty. (Excludes
Trans). The Allison® Transmission and TCM will
be warrantied by Allison® and will have to be
taken to an Allison® Authorized Distributor and
Dealer Location for repair or replacement.
Find an Allison® Authorized Service Facility near
you by searching the Sales + Service Locator.
Click on:
Sheet Metal: Corrosion coverage is for the first
3 years or 36,000 miles, whichever comes first.
Sheet Metal: Rust-through coverage is for the
first 6 years or 100,000 miles, whichever comes
first.
Page 32
November, 2019
Bulletin No.: 18-NA-366
Wireless Charging
5183776
The Wireless Charging system for mobile devices is
located on the storage tray on top of the center console
(Crew Cab bucket seat equipped models only).
1. The vehicle must be ON or Retained Accessory
Power (RAP) must be active.
2. Remove all objects from the charging pad.
3. Place the device, face up, against the rear
alignment rib on the charge pad.
4. The charging symbol will appear on the
infotainment screen when charging. If the device is
not charging, remove it for 3 seconds and rotate it
180 degrees.
Special Tools
The following new tools were released for the 2019
Silverado 4500HD, 5500HD and 6500HD chassis cab
medium duty trucks:
Special Tools — Tool Number and Description
Tool Number
Description
EN-52539
Holder, Fan Clutch Pulley — Engine L5D and L5P
EN-52538
Compressor, Tensioner Strut — Engine L5D
J-39197-21
T&B Flex Connector (incl. J-39197-1 x3) — Electrical for Allison Transmission
J-39197-22
0.062 AMP Male Connector (incl. J-39197-2 x3) — Electrical for Allison
Transmission
J-39197-23
280 Series Flex Connector (incl. J-39197-3 x3) — Electrical for Allison
Transmission
J-47277
4th Gen TCM Terminal Test Probe (Orange) — Electrical for Allison Transmission
GE-52582
Drain Hose (w/ Quick Connect and Valve) — Engine Cooling
DT-52713
Transfer Case 7-way Breakout Harness — Driveline
DT-52709
Pinion Seal Installer (Front) — Driveline Dana
DT-52710
Pinion Seal Installer (Rear) — Driveline Dana
PN 20-2977-2 (8-Lug, 19.5 inch Stud Kit)
Wheel Balancer Adapter — Will Ship Essential
Bulletin No.: 18-NA-366
November, 2019
Page 33
Special Tools — Tool Number and Description (cont'd)
Tool Number
Description
Special Tool Loan Program
CH-52708
Parking Brake Adjustment Tool — Brakes
CH-52707
Installer / Remover, Bushing (1.35" O.D.) — Chassis
CH-52706
Installer, 1.39" I.D. x 1.76" O.D. — Chassis
CH-52705
King Pin Bushing Service Kit — Chassis
DT-52739
Transfer Case Support Adapter — Transfer Case (Meritor)
Training Course
Training Courses — Description — Number and Course Name
Description
Number and Course Name
New Model Features
#90319.50W: 2019 Medium Duty Silverado 4500HD, 5500HD,
& 6500HD New Model Features
Version Information
Version
2
Modified
Released December 18, 2018
Revised October 22, 2019 —Added the Exhaust Aftertreatment System Component
Names and their identifiers from the Power and Signal Master Electrical Component List.
Trademark Footnotes
ACDelco® is a registered trademark of General
Motors LLC
Allison® is a registered trademark of Allison
Transmission
– Emergency Vehicle Series™ is a trademark of
Allison Transmission
– Highway Series™ is a trademark of Allison
Transmission
– Motorhome Series™ is a trademark of Allison
Transmission
– Rugged Duty Series™ is a trademark of Allison
Transmission
Android™ is a trademark of Google LLC .
Android Auto™ is a trademark of Google LLC
Apple® is a registered trademark of Apple Inc.
Bluetooth® is a registered trademark Owned by
Bluetooth SIG, Inc.
Bosch® is a registered trademark of Robert Bosch
GmbH, Germany
CarPlay™ Software Feature is a trademark of
Apple Inc.
Duramax® is a registered trademark of General
Motors LLC (United States)
Duramax™ is a trademark of General Motors LLC
Goodyear® is a registered trademark of The
Goodyear Tire & Rubber Company
Hydro-Max™ is a trademark of Robert Bosch
GmbH, Germany
LTE™ is a trademark of the European
Telecommunications Standards Institute (ETSI)
OnStar® is a registered trademark of OnStar, LLC
Speedpass+™ is a trademark of Exxon Mobil
Corporation
Wi-Fi® is the registered trademark of the Wi-Fi
Alliance
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a
job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.
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