Transmission Control Module (TCM) Adaptation - 8HP45/845RE/8HP70/8HP90: Notes
The TCM or Transmission Control Module Assembly (TCMA) controls the fluid pressure and fill time of each clutch pack to give optimal shift quality. As the clutches wear, the TCM or TCMA will adapt and make adjustments to keep the shift quality consistent over the life of the vehicle. The initial clutch filling pressure and fill times are set at the factory. When a transmission assembly or transmission component is replaced, or when the adaptation values are reset, the adaptation values must be relearned. This procedure should also be followed when it is suspected that a vehicle has not been driven in a manner that encourages clutch adaptation learning in highway or city driving conditions.
The scan tool for some 8-Speed Transmissions now has a QUICK LEARN routine. If the QUICK LEARN routine is available on the scan tool for the application you are working on, then the TCM ADAPTATION PROCEDURES below do not need to be performed.
QUICK LEARN PROCEDURE
2015 model year vehicles equipped with the 845RE (Sales Code DFL) already contain software in the TCM to enable the Quick Learn procedure. However, 2014 model year vehicles with the 845RE require the Transmission Control Module to be updated to the latest software level.
The scan tool software must be at the newest revision to perform this procedure.
The QUICK LEARN PROCEDURE requires that the Transmission fluid temperature be at least 55°C (131°F).
- Drive the vehicle briefly to ensure all clutches have been engaged at least twice. Keep the engine running throughout the remainder of this procedure.
- With the scan tool, activate the RESET ADAPTIVE VALUES routine.
- With the scan tool, activate the QUICK LEARN routine and follow the on-screen instructions. This procedure requires about 2-5 minutes to complete.
TCM ADAPTATION PROCEDURES
The two procedures to relearn these values are called Fast Filling Adaptation and Standard Clutch Filling Adaptation. Depending on the repair or complaint, one or both procedures must be performed as described below.
Performing a reset of the Transmission Adaptation values does not automatically trigger the TCM to relearn the Adaptation values. If a reset is performed, both procedures must be performed to restore optimal shift quality. Do not reset these values unless specifically instructed to do so.
This procedure does not need to be performed if the existing TCM or TCMA is reflashed and that was the only repair performed.
One or both TCM Adaptation procedures should be performed depending on the situation. Failure to perform these procedures when required could cause shift quality issues.