General Motors (GM) has announced a safety defect affecting the transmission control valve in certain Chevrolet, GMC, and Cadillac vehicles equipped with diesel engines. The issue involves excess wear on the transmission control valve, which could lead to a gradual loss of pressure. This defect has the potential to cause harsh shifting, and in rare cases, a momentary lock-up of the rear wheels.

The Affected Vehicle Models Are:

GM first became aware of this issue in June 2024 through the company’s Speak Up for Safety (SUFS) program, after a customer claimed that the rear wheels of a 2021 GMC Sierra 2500 HD pickup allegedly locked up while towing a trailer. The incident caused property damage to both the vehicle and the trailer. This report prompted GM to open a new investigation.

Previously, GM had already investigated the condition, finding that excessive wear in the transmission control valve could cause harsh downshifting and, in some cases, a momentary lock-up of the rear wheels. Earlier tests and analyses suggested that the lock-up was unlikely to lead to loss of vehicle control, and no accidents or injuries were reported at the time.

In July, the National Highway Traffic Safety Administration (NHTSA) notified GM that its Vehicle Owner Questionnaire (VOQ) monitoring process had flagged additional reports that could be related to this issue. GM’s investigators conducted an extensive analysis of these reports and reviewed comprehensive field data, identifying 1,888 field reports alleging a potential lock-up condition. Further examination revealed eleven specific incidents where the vehicles veered off the road, causing minor property damage. There were also three minor injuries reported, although none were linked to a collision.

Based on these findings, GM’s Safety Field Action Decision Authority (SFADA) decided in October to initiate a safety recall.

To address the defect, GM dealers will install updated transmission control module software. This software will monitor valve performance and detect signs of excess wear approximately 10,000 miles before a wheel lock-up condition could occur. If excess wear is detected, the software will limit the transmission to fifth gear, effectively preventing a wheel lock-up scenario, which typically happens during a downshift from eighth gear. Additionally, the vehicle’s instrument panel will display a service engine light and a reduced propulsion warning message to alert the driver. GM’s number for this recall is N242454440 and the NHTSA campaign number is 24V-797.