Transmission Control Module (TCM) Communication Fault
There’s a communication issue with the Transmission Control Module.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
Your car's brain can't talk to the part that controls the transmission, which could mean bad wiring or a faulty module.
What the computer is actually seeing
The engine control unit (ECU) expects to receive data from the TCM over the CAN bus. When it doesn't get that data within a certain timeframe, it triggers the code. This time could be around 100 milliseconds without communication.
What a healthy reading looks like
Normal CAN communication should have a signal voltage of 2.5V to 5V; a fault will show no communication or a consistent low signal.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check the vehicle's battery voltage; it should be between 12.4V and 12.6V. If low, charge the battery before further diagnosis.
- 22. Inspect all wiring and connectors to the Transmission Control Module for damage, corrosion, or loose connections. Repair as necessary.
- 33. Use a scan tool to check for other codes; if found, address them as they may relate to the communication issue. Clear codes and see if it returns.
- 44. Verify CAN bus communication; check for proper voltage levels (2.5V to 5V) on the pins that connect the TCM. If there's no signal, the issue may be in the wiring.
- 55. If all wiring checks out and the battery is good, test or swap the TCM if necessary. Ensure it's programmed for the vehicle before installation.
Common causes
- Faulty Transmission Control Module (TCM)
- Wiring issues between the ECU and TCM
- Corroded connectors
- Faulty CAN bus wiring
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's still drivable, but you'll notice shifting issues; fix it soon to avoid further damage.
Will this code come back after clearing?
Yes, if the underlying issue isn't fixed, the code will likely return.
Why does this code pair with other codes?
Other codes often indicate related issues in the transmission system; they can help pinpoint the root cause.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →