Theory Of Operation
The Transmission Control Module (TCM) requests torque reductions over the CAN bus during a transmission shift to improve shift quality. The TCM verifies that the Powertrain Control Module (PCM) has performed the requested torque reduction by monitoring the response to the request. If the response is not within a specified tolerance, the TCM increments a counter, and if this counter reaches a threshold, the DTC sets.
It may be possible for this DTC to set if the PCM disregards the torque reduction request due to poor engine performance. If the engine is running rough or is about to stall out, the PCM may ignore the torque reduction request in an effort to prevent an engine stall out. Always address any drivability issues prior to diagnosing the transmission.
This is not a Torque Converter Clutch DTC. This DTC indicates that the TCM did not receive a response from the PCM that a torque reduction request was carried out.