20-NA-050

Service Bulletin
Bulletin No.:
20-NA-050
Date:
May, 2022
TECHNICAL
Subject:
Rough Shifting, Surging, Jerk/Lurch While Accelerating from a Stop Just After Shifting
Out of 4LO, Service 4WD Message Displayed on the Driver Information Center (DIC),
Malfunction Indicator LAMP (MIL) Illuminated - DTCs P17D4, P215B, P279A and/or
P279B Set
Brand:
Model:
Cadillac
Model Year:
from
to
Escalade
2014
2020
Colorado
2015
2019
Silverado
2014
2018
2019
2019
Silverado
2500/3500
2019
2020
Silverado 1500
2020
2020
2014
2020
Canyon
2015
2019
Sierra
2014
2018
Sierra 1500
(New Model)
2019
2019
Sierra 2500/3500
2019
2020
Sierra 1500
2020
2020
Yukon
2014
2020
VIN:
from
to
Engine:
Transmission:
Silverado LD
Silverado 1500
(New Model)
Chevrolet
Silverado
(New Model - 12th
VIN Digit=7)
Suburban
Tahoe
Sierra Limited
GMC
Involved Region or Country
North America, Europe, Russia, Middle East, Israel, Chile, Columbia, Ecuador, Paraguay,
Uruguay, Peru, Japan, South Korea, China and Thailand.
Additional Options (RPOs)
NQF: TRANSFER CASE-ELECTRIC SHIFT CONT, TWO SPEED, ALUM
NQH: TRANSFER CASE-ACTIVE, TWO SPEED, SWITCH ACTIVATED, ALUM
NQ6: TRANSFER CASE-2 SPD, ACTIVE, PART TIME 4WD, L/H DROP, LOW
RATIO 2.72:1
Copyright 2022 General Motors LLC. All Rights Reserved.
Page 2
May, 2022
Bulletin No.: 20-NA-050
Condition
Some Customers may comment on one or more of the following conditions:
• Rough shifting
• Surging
• Jerk/lurch, especially while accelerating from a stop just after shifting out of 4LO
• Service 4WD message on the DIC
• MIL illuminated
Some technicians may find one or more of the following DTCs set in the Engine Control
Module (ECM):
• P17D4: Transfer Case Neutral Range Detected in High or Low Range
• P215B: Vehicle Speed - Output Shaft Speed Not Plausible Vehicle Speed - Output
Shaft Speed Not Plausible
• P279A: Transfer Case High Range Incorrect Ratio
• P279B: Transfer Case Low Range Incorrect Ratio
Cause
This condition may be caused by the customer improperly shifting the transmission out of
neutral or applying the gas pedal before the transfer case shifts completely out of 4LO.
Correction
Advise customer to refrain from shifting the vehicle out of neutral or applying the gas
pedal before the transfer case shifts out of 4LO. The vehicle owner’s manual provides the
correct procedure that should be followed when shifting the transfer case out of 4LO.
Correction Repair Procedure:
1. Engage Ignition On.
2. Engage Park Brake.
3. Engage Transmission Neutral.
4. Clear DTCs with Scantool.
5. Switch vehicle to power mode OFF and wait for 2 minutes to allow for the bus and
ECM to sleep.
6. Start vehicle.
7. Confirm no codes or Service 4x4 message on DIC is present.
8. Shift Transfer Case through 2HI, 4HI, 4LO, N and back to 2HI, to confirm the
Transfer Case Range shift is functioning properly.
If the Transfer Case cannot shift through all of the modes noted above or if there are any
abnormal conditions present, perform the diagnostics within Service Information.
Parts Information
No parts are required for this repair.
Warranty Information
For vehicles repaired under the Bumper-to-Bumper
coverage (Canada Base Warranty coverage), use the
following labor operation. Reference the Applicable
Warranties section of Investigate Vehicle History (IVH)
for coverage information.
Labor Operation
Description
Labor Time
3087118*
Clear DTCs and Cycle Transfer Case Modes
0.3 hr
*This is a unique Labor Operation for Bulletin use only.
Version
2
Modified
Released March 03, 2020
Revised April 28, 2022 - Change Warranty Information from Powertrain to Bumper to
Bumper.
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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