General Motors has issued a service update to address a problem related to the Transmission Control Module in certain examples of the 2020 and 2021 model-year C8 Corvette Stingray.

The problem: in affected vehicles, the Transmission Control Module (TCM), after detecting a loss of communications, may incorrectly clear the “loss of communications” Diagnostic Trouble Codes upon switch off. If the loss of communication with the TCM persists, the vehicle may not detect it again when the vehicle is turned back on.
If this were to happen, the transmission could operate in a default mode with no Diagnostic Trouble Codes reported and the Malfunction Indicator Light not illuminated.

The hazards:

While this issue does not pose a safety hazard, it could prevent the vehicle’s transmission from performing as intended and should thus be addressed as soon as possible. This problem could also prevent the transmission from producing DTCs or an MIL if something more serious were wrong with the unit.

The fix:

This problem can be remedied via an over-the-air software update.
Owners can also have their vehicle serviced at a GM dealer to receive the software updates,
although installing them on the vehicle’s touchscreen is a fairly straightforward process.

Affected components: Transmission Control Module (TCM).

Affected vehicles:

• 2020 and 2021 Corvette Stingray

Owners should: Owners can accept the terms and conditions for over-the-air software updates in their vehicle’s touchscreen and perform the update themselves, or take the vehicle to a dealer for service.
Owners with questions or concerns regarding this service bulletin can also reach out to GM using the contact information provided below.

• General Motors Service Update Number: 212336960

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True Custom Performance Tuning