P0866 OBD-II: TCM Communication Circuit High

P0866 Severity

Urgent

Should you fix P0866 yourself?

Identifying an OBD code is just the start of a complete diagnostic routine. Most trouble codes are caused by a sensor reporting a value that is out of range. Just replacing a sensor may not fix underlying issues. Be sure to understand the code, the part or system in your car that the code refers to, and the risks of delaying professional repair.

Proper diagnosis will save you time and money on unnecessary repairs.

Urgent codes indicate immediate action is necessary. These are urgent and significant malfunctions that can cause severe damage to the vehicle or harm the driver and passengers.

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What causes OBD-II fault code P0866?

If the Transmission Control Module (TCM) cannot communicate with other modules or the engine control module (PCM) can not communicate with the PCM, code P0866 will be set.

OBD II Fault Code

OBD II P0866

OBD-II Code Transmission may not shift properly is defined as a TCM Communication Circuit High

If the Transmission Control Module (TCM) cannot communicate with other modules or the engine control module (PCM) can not communicate with the PCM, code P0866 will be set.

Transmission may not shift properly Symptoms

Increased fuel consumption
Transmission may not shift properly

Common Problems That Trigger the P0866 Code

Transmission Control Module (TCM) failure
Wiring issue

OBD Code Resources

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OBD II Fault Code

OBD II P0866

OBD-II Code Transmission may not shift properly is defined as a TCM Communication Circuit High

If the Transmission Control Module (TCM) cannot communicate with other modules or the engine control module (PCM) can not communicate with the PCM, code P0866 will be set.

Transmission may not shift properly Symptoms

Increased fuel consumption
Transmission may not shift properly

Common Problems That Trigger the P0866 Code

Transmission Control Module (TCM) failure
Wiring issue

P0866 OBD-II: TCM Communication Circuit High

Should you fix P0866 yourself?

What causes OBD-II fault code P0866?

Need a P0866 diagnosis? Trust our experts.

OBD II Fault Code

Transmission may not shift properly Symptoms

Common Problems That Trigger the P0866 Code

OBD Code Resources

Ask our experts about P0866.

Other OBD-II Codes

OBD II Fault Code

Transmission may not shift properly Symptoms

Common Problems That Trigger the P0866 Code