P2637 - Torque Management Feedback Signal 'A'
- Faulty Engine Control Module (ECM)
- Faulty Transmission Control Module (TCM)
- Engine Control Module (ECM) software update
- Transmission Control Module (TCM) software update
- Engine Control Module (ECM) harness is open or shorted
- Engine Control Module (ECM) circuit poor electrical connection
- Engine Light ON (or Service Engine Soon Warning Light)
To improve shift feel, the Transmission Control Module (TCM) may request that the Engine Control Module (ECM) reduce engine torque during shift events. When such a request is received, the ECM responds by retarding the base ignition timing and notifying the TCM that the request has succeeded. If the ECM is unable to comply with the request, the ECM sends the TCM a message that the request has failed.
The torque reduction request is sent to the ECM through a communication network called the controller area network (CAN). Two circuits are used to communicate CAN data between the ECM and TCM.
A fault in the CAN will not cause the ECM to set the Diagnostic Trouble Codes (DTC). If a CAN fault occurs, other DTCs will set before this code.
The ECM set the OBDII code when the TCM receives a torque reduction failure message from the ECM.