21NA275

Bulletin No.:
Service Bulletin
Date:
21-NA-275
January, 2022
TECHNICAL
Subject:
Brand:
Rear Wheel Lock Up, ABS Event, Loud Bang and a Flashing “D” on Driver Information
Center (DIC) when Lightly or Moderately Accelerating, Forcing an 8-7 or 8-6 Downshift
Model:
GMC
from
to
Engine:
Transmission:
(Automatic)
2020
2021
CT6
2019
2021
Escalade
Models
2021
2021
LM2
MQC
Silverado
1500
2020
2021
LM2
MQB
Silverado
2500HD/
3500HD
2020
2021
L5P
MGM, MGU
Suburban
2021
2021
LM2
MQC
Tahoe
2021
2021
LM2
MQC
Sierra 1500
2020
2021
LM2
MQB
Sierra
2500HD/
3500HD
2020
2021
L5P
MGM, MGU
Yukon
2021
2021
LM2
MQC
CT5
Chevrolet
VIN:
to
CT4
Cadillac
Model Year:
from
MQA
LSY
MHS
MHS
—
—
Involved Region or Country
North America, Uzbekistan, Russia, Middle East, Israel, Palestine, Bolivia, Chile,
Colombia, Ecuador, Paraguay, Peru, Uruguay, Venezuela, China
Condition
Some customers may comment on the following conditions while lightly to moderately
accelerating, forcing an 8-7 or 8-6 downshift between 64-96 km/h (40-60 mph) with the
transmission at operating temperature:
• Rear wheel/tire lockup or an ABS event
• Loud bang
• Very hard 8-7 or 8-6 downshift
• Feeling of hitting a large pothole or large speed bump
• Flashing “D” on the DIC
Cause
This condition may be caused by an internal control valve body issue.
Correction
Replace the valve body assembly. Refer to Control Valve Body Replacement in SI.
Copyright 2022 General Motors LLC. All Rights Reserved.
Page 2
January, 2022
Bulletin No.: 21-NA-275
Parts Information
Use the VIN and refer to the GM Electronic Parts
Catalog (EPC) to determine the proper part to order.
Causal
Part
Description
Part
Number
Qty
X
VALVE, CONT
(CT4, CT5, CT6)
24044192
1
X
VALVE, CONT
(2020 T1 LD)
24044189
1
X
VALVE, CONT
(First Design 2020
T1 HD)
24041375
1
X
VALVE, CONT
(Second Design
2020 and 2021
T1 HD)
24044274
1
X
VALVE
ASM,- CONT
24047334
1
X
VALVE
ASM,- CONT
24043770
1
X
VALVE
ASM,- CONT
24043767
1
N/A
Transmission
Fluid
19352619
(U.S.A.)
19352620
(Canada)
8
Warranty Information
For vehicles repaired under the Emission coverage,
use the following labor operation. Reference the
Applicable Warranties section of Investigate Vehicle
History (IVH) for coverage information.
Labor Operation
Description
Vehicle
Labor Time
8463690
Diagnostic Time and Test
Drive
All
0.5 hr
Add
CT4
Add
CT5
Add
CT6
Add
Silverado 1500
Add
Add
Control Valve Body
Replacement
Sierra 1500
Silverado 2500HD/3500HD
Add
Sierra 2500HD/3500HD
Add
Suburban
Add
Tahoe
Add
Yukon
Version
1
Modified
Released January 25, 2022
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.
1.7 hrs
1.5 hrs
3.4 hrs
1.5 hrs
2.6 hrs
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