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 – 2019-2021 Cadillac Chevrolet GMC

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Copyright 2022 General Motors LLC. All Rights Reserved. Service Bulletin Bulletin No.: 21-NA-275 Date: August, 2022 TECHNICAL Subject: 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 Brand: Model: Model Year: VIN: Engine: Transmission: from to from to (Automatic) Cadillac CT4 2020 2021 — — LSY MQA CT5 MHS CT6 2019 2021 MHS Escalade Models 2021 2021 LM2 MQC Chevrolet Silverado 1500 2020 2021 LM2 MQB Silverado 2500HD/3500HD 2020 2021 L5P MGM, MGU Suburban 2021 2021 LM2 MQC Tahoe 2021 2021 LM2 MQC GMC Sierra 1500 2020 2021 LM2 MQB Sierra 2500HD/3500HD 2020 2021 L5P MGM, MGU Yukon 2021 2021 LM2 MQC Involved Region or Country North America, Uzbekistan, Russia, Middle East, Israel, Palestine, Bolivia, Chile, Colombia, Ecuador, Paraguay, Peru, Uruguay, Venezuela, China, Australia, New Zealand. 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. Page 2 August, 2022 Bulletin No.: 21-NA-275 Important: Service agents must comply with all International, Federal, State, Provincial, and/or Local laws applicable to the activities it performs under this bulletin, including but not limited to handling, deploying, preparing, classifying, packaging, marking, labeling, and shipping dangerous goods. In the event of a conflict between the procedures set forth in this bulletin and the laws that apply to your dealership, you must follow those applicable laws. 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 (Second Design 2020 and 2021 T1 HD) 24044274 1 X VALVE, CONT (First Design 2020 T1 HD) 24047334 1 X VALVE ASM,- CONT 1 X VALVE ASM,- CONT 24043770 1 X VALVE ASM,- CONT 24043767 1 N/A SEAL, A/TRNS AUX FLUID PUMP 24047734 1 N/A Transmission Fluid 19352619 (U.S.A.) 19352620 (Canada) As Required 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 8486158* Test Drive/ Diagnostic/ Control Valve Body Replace CT4 2.2 hrs CT5 CT6 2.0 hrs Silverado 1500 3.9 hrs Sierra 1500 Silverado 2500HD/ 3500HD 2.0 hrs Sierra 2500HD/ 3500HD Escalade 3.1 hrs Suburban Tahoe Yukon *This is a unique Labor Operation for bulletin use only. Version 3 Modified Released January 25, 2022 Revised May 19, 2022 – Updated Parts Information section and added Unique Labor Operation number in Warranty Information section and added more Keywords. Revised August 23, 2022 – Added an Important statement and updated Transmission Fluid Quantity in the Parts Information section. Additional SI Keywords: shift, down, brake, braking, unwanted 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. WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

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