20NA038

Service Bulletin
Bulletin No.:
20-NA-038
Date:
April, 2021
INFORMATION
Subject:
Information on Active Fuel Management (AFM) and Dynamic Fuel Management (DFM)
Usage
This bulletin replaces PIP5663. Please discard PIP5663.
Brand:
Cadillac
Model:
VIN:
from
Engine:
to
CTS
2016
2019
6.2L (LT4)
CT6
2016
2020
6.2L (LTA)
Escalade
2015
2021
5.3L (L83)
6.2L (L86)
3500/4500
Medium
Duty (LCF)
2020
2020
6.6L (L8T)
Camaro
2016
2021
6.2L (LT1, LT4)
2014
2019
6.2L (LT1,
LT4, LT5)
2020
2021
6.2L (LT2)
Express
2018
2021
4.3L (LV1),
6.6L (L8T)
Silverado
2014
2018
Corvette
Chevrolet
Model Year:
from
—
—
4.3L (LV1, LV3)
5.3L (L83)
6.2L (L86)
Silverado
1500 (New
Model)
2019
2019
4.3L (LV3)
5.3L (L82, L84)
6.2L (L87)
Silverado LD
2019
2019
5.3L (L83)
Silverado
1500
2020
2021
4.3L (LV3)
5.3L (L82, L84)
6.2L (L87)
Silverado
2500/3500
2020
2021
6.6L (L8T)
Suburban
2015
2021
5.3L (L83, L84)
6.2L (L86, L87)
Tahoe
2015
2021
5.3L (L83, L84)
6.2L (L86, L87)
Copyright 2021 General Motors LLC. All Rights Reserved.
Transmission:
to
—
Page 2
Brand:
GMC
April, 2021
Model:
Model Year:
Bulletin No.: 20-NA-038
VIN:
from
Engine:
from
to
Savana
2018
2021
4.3L (LV1),
6.6L (L8T)
Sierra
2014
2018
4.3L (LV1, LV3)
5.3L (L83)
6.2L (L86)
4.3L (LV3)
5.3L (L82, L84)
6.2L (L87)
to
Sierra 1500
(New Model)
2019
2019
Sierra
Limited
2019
2019
Sierra 1500
2020
2021
4.3L (LV3)
5.3L (L82, L84)
6.2L (L87)
Sierra
2500/3500
2020
2021
6.6L (L8T)
Yukon
Models
2015
2021
5.3L (L83, L84)
6.2L (L86, L87)
Involved Region or Country
—
Transmission:
—
4.3L (LV3)
5.3L (L83)
6.2L (L86)
North America, Europe, Uzbekistan, Russia, Middle East, Iraq, Israel, Palestine,
Argentina, Brazil, Bolivia, Chile, Colombia, Ecuador, Paraguay, Peru, Uruguay,
Venezuela, Japan, Cadillac Korea (South Korea), GM Korea Company, China, Taiwan,
Thailand, Singapore, Philippines, Egypt, Other Africa, South Africa
AFM (Active Fuel Management)
To provide maximum fuel economy under light load driving conditions, the engine control
module (ECM) will command the cylinder deactivation system ON to deactivate engine
cylinders 1, 7, 6, and 4, switching to a V4 mode. The engine will operate on 8 cylinders, or
V8 mode, during engine starting, engine idling, and medium to heavy throttle applications.
AFM – active fuel management strategy which deactivates the lifters on specific
cylinders. On V8 engines, it deactivates half of the cylinders (1,7,6 and 4) and on V6
engines, it deactivates only 2 of the cylinders (3 and 6). For LTA and LT2 engines, the
deactivation occurs on cylinders 2, 3, 5 and 8.
LOMA – lifter oil manifold assembly is only used on legacy AFM applications
DFM (Dynamic Fuel Management)
Information
Dynamic Fuel Management (DFM) is recognized as active fuel management technology
with the additional ability to deactivate any combination of cylinder valves for an internal
combustion engine. This technology combines millisecond-accurate torque control with
cylinder deactivation to optimize fuel consumption of spark ignited engines. The control of
every cylinder event optimizes engine operation such that peak efficiency is obtained
throughout the range of engine operation. DFM extends cylinder deactivation to all
cylinders, which allows for a large variety of firing sequences. DFM can have rotating
cylinder deactivation patterns as well as fixed patterns. For rotating patterns, which
cylinders are being deactivated can change with each subsequent engine cycle.
Transitions between firing sequences is done in a continuous fashion, making the
transitions seamless and transparent to the vehicle operator.
DFM – dynamic fuel management which can deactivate the lifter on any cylinder at any
time. Unlike AFM, this can result any many different types of firing patterns, some of
which are fixed patterns (like ¼, ½, ¾) and others which are rotating (like 1/5, 1/3, 2/5, 2/
3). This is only available on small block engines (L84 and L87).
OCV – oil controlled valve is only used on small block engines. These provide faster
response times than LOMA and are required for DFM (on L84 and L87). OCVs are also
used on L82 for AFM.
Refer to the AFM/DFM Usage Chart below.
Bulletin No.: 20-NA-038
April, 2021
Page 3
AFM/DFM Usage Chart
Vehicles
AFM
VLOM
4 Cylinder
Deactivation
DFM. OCV's
FDFM
None
Notes
CTS LT4
Yes
Yes
No
No
—
Always active
CT6 LTA
No
Yes
No
No
—
—
Camaro LT1
Yes
Yes
No
No
—
Automatic only. AFM not
active with Manual trans
Camaro LT4
Yes
No
No
No
—
Has the hardware, Not
active
Corvette LT1
Yes
Yes
No
No
—
Auto Trans active,
Manual Trans active in
ECO only
Corvette LT2
No
Yes
No
No
—
—
No
—
Auto Trans active,
Manual Trans active in
ECO only
Corvette LT4
Yes
Yes
No
Corvette LT5
No
No
No
No
Yes
No hardware on LT5
Escalade L83, L86
Yes
Yes
No
No
—
—
Escalade L87
No
No
Yes
Yes
—
—
Express/Savana LV1
No
No
No
No
—
No hardware on LV1
Silverado/Sierra
L83, L86
Yes
Yes
No
No
—
—
Suburban/Tahoe/Yukon
L83, L86
Yes
Yes
No
No
—
—
Suburban/Tahoe/Yukon
L84, L87
No
No
Yes
Yes
—
—
Silverado/Sierra L82
No
Yes
Yes
No
—
—
Silverado/Sierra L84
No
No
Yes
Yes
—
—
Silverado/Sierra L87
No
No
Yes
Yes
—
—
Silverado/Sierra L82,
L84 with RPO YK9 Only
Yes
No
Yes
No
—
Hardware is there ECM
and Software not
capable
Silverado/Sierra HD L8T
No
No
No
No
—
No hardware on L8T
Silverado/Sierra LV1
No
No
No
No
—
—
Silverado/Sierra LV3
Yes
Yes
No
No
—
—
3500/4500 Medium
Duty (LCF)
No
No
No
No
—
No hardware on L8T
Information
Note: Beginning in March 2021, most 2021 Silverado
1500 and 2021 Sierra 1500 pickups equipped with L82
MYC 6-speed and L84 MQE 8-Speed will be produced
without Active Fuel Management/AFM (L82), or
Dynamic Fuel Management/DFM (L84). The engines
will still be equipped with the hardware, but the ECM
and software will not be capable of activating this
technology.
Pickups equipped with L82 MYC or L84 MQE, which
are produced without AFM or DFM function, will be
identified with New RPO YK9 (Not Equipped with
Cylinder Deactivation).
Internal components related to AFM or DFM function
will be present in engines; wiring, connectors, and
fuses will be present in vehicles with RPO YK9. The
ECM will not be capable of activating the cylinder
deactivation technology.
Page 4
April, 2021
Bulletin No.: 20-NA-038
Parts Information
No parts are required for this repair.
Version
2
Modified
Released February 26, 2020
April 08, 2021 – Added 2021 Model Year to certain models, added additional vehicles to
AFM/DFM Usage Chart and added the Information section.
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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