Certain 2017 GMC Sierra, Yukon and Yukon XL vehicles equipped with an 8-speed automatic transmission may have a condition where a false failure action is being taken when it is not required. This condition can result in the transmission holding the last known safe gear for 6 seconds.
A malfunction indicator lamp is set when this default happens more than 2 times, and reduced propulsion can happen for all 8-speed transmission applications. The correction involves reprogramming the TCM (transmission control module).
Do not attempt to order the calibration number from GM Customer Care and Aftersales. The calibration numbers required for this service procedure are programmed into control modules via a Multiple Diagnostic Interface (MDI) with the calibration update.
Do not program a control module unless directed to by a service procedure. If the control module is not properly configured with the correct calibration software, the control module will not control all of the vehicle features properly. Ensure that the programming tool is equipped with the latest software and is securely connected to the data link connector, to avoid module damage.
Install the EL-49642 SPS programming support tool to maintain system voltage during programming. If not available, connect a fully charged 12V jumper or booster pack that is disconnected from an AC voltage supply. Do not connect a battery charger.
Turn off or disable systems that may place a load on the vehicle battery such as interior lights, daytime running lights, HVAC, radio, etc.
During programming, follow the SPS prompts for the correct ignition switch position.
Reprogram the transmission control module. Refer to transmission control module programming and set-up in the service manual.