Adjustment of Shifting ,Performance, Automatic Transmission

Fault Symptom
Diagnostic trouble codes P1786, P1787 or P1788 generated in the Traction Control Module (TCM) system.
Hard shifting when the TCS is activated.

Diagnostic Procedure
1. If diagnostic trouble codes have been generated in the TCS system, deal with them first. If no trouble codes have been generated, proceed as follows.
Drive the car on the road and check whether trouble codes are generated afresh in the Traction Control Module (TCM) system. If they are, proceed as follows.

CAUTION: To activate the TCS function, the car can be raised on a garage lift. Proceed with the outmost caution if this method is chosen. If only the front of the car is raised and supported on stands, the handbrake must always be applied and nobody should stand in front of the car or beside the front wheels while the test is in progress. Speed should be restricted to the minimum possible above 4 km/h.

2. Use the ISAT (scan tool) to communicate with the Traction Control Module (TCM) system and select "TCS ACTIVE" in the "READ ON/OFF" menu.
Activate the TCS by engaging a gear and driving the front wheels while the front assembly of the car is raised. Check whether the ISAT (scan tool) display text changes from TCS OFF to TCS ON at the same time as the TCS lamp lights up.
If it does not, check the cable between pin 12 of the TCS control module and pin 4 of the Traction Control Module (TCM) control module for continuity/shorting.
3. Use the ISAT (scan tool) to communicate with the Traction Control Module (TCM) system and select "TCS THROTTLE POSITION" in the "READ FUNCTIONS" menu.
Check that the throttle position is about 70-92% when the wheels are stationary and that it changes to a much lower figure when the speed of the front wheels exceeds 4 km/h.
If it does not, check the cable between pin 4 of the TCS control module and pin 15 of the Traction Control Module (TCM) control module for continuity/shorting.