Most vehicles have thousands of sensors, control modules and connection points that relay information to the ECU about what the vehicle is doing. A P0863 DTC means that there is a communication issue somewhere between the transmission control module (TCM) and the engine control unit (ECU).
How Serious is the Code?
The P0863 diagnostic trouble code is quite serious, and the lack of communication between the ECU and the transmission control module can cause a number of drivability issues.
Symptoms of a P0863 include:
- Harsh, delayed or erratic shifting
- Limp mode
- Damaged wiring and/or corroded connectors
- Faulty transmission control module
- Failed engine control module
- Software issues
How to Diagnose the Code?
The first step to diagnosing a P0863 OBDII trouble code, is to check all of the wiring on the transmission wiring harness for damaged wires and corroded or broken connectors. If no problems are found, and there are no manufacturer TSB’s about software or wiring updates, then the transmission control module and possibly the ECU should be checked.
What Repairs Will Fix P0863?
- Repair or replace damaged wiring on the transmission wiring harness
- Replace or repair broken/corroded connectors
- Replace transmission control module
- Replace engine control unit
- Update TCM/ECU software