The P0861 code in your 2021 Chrysler 300 indicates the transmission control module (TCM) communication circuit is providing lower voltage than expected. This affects the TCM's ability to communicate with other vehicle systems.
Understanding TCM Communication
The 300's TCM communicates over the CAN bus network with the PCM, shifter, and other modules. Low voltage on the communication circuit can cause incomplete or failed data exchange, affecting transmission operation.
Common Causes of P0861
- Short to ground in CAN bus wiring
- High resistance in communication circuit
- TCM internal circuit failure
- Connector corrosion
- Power supply issues to TCM
- Ground connection problems
Symptoms of Low Communication Voltage
- Multiple system warnings
- Check engine light on
- Transmission may enter limp mode
- Shift quality issues
- Gauge cluster errors
- Various systems may be affected
Network-Wide Effects
CAN bus issues can affect multiple systems. P0861 at the TCM may trigger codes in other modules and cause seemingly unrelated symptoms throughout the vehicle.