Engine / Transmission Interface Fault
There’s an issue with the communication between the engine and transmission control modules.
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)
This fault means the engine and transmission are having trouble talking to each other, which can make the vehicle shift badly or not at all.
What the computer is actually seeing
The engine control module (ECM) and transmission control module (TCM) are designed to communicate over a data link. If the TCM doesn’t receive expected data packets from the ECM within a specific time frame (like 100 ms), this code triggers.
What a healthy reading looks like
Communication packets between ECM and TCM should be consistent and within 0.5 seconds of each other. Voltage levels on data lines should be between 2.5V and 3.5V when active.
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. Inspect the wiring harness between the ECM and TCM for visible damage or corrosion. Is the wiring in good condition? (Yes: Proceed to step 2, No: Repair the wiring)
- 22. Check all connectors related to the ECM and TCM for signs of corrosion or loose connections. Are the connections secure? (Yes: Proceed to step 3, No: Clean/re-seat connectors and retest)
- 33. Verify voltage levels on the data line using a multimeter. Are the voltage levels between 2.5V and 3.5V? (Yes: Proceed to step 4, No: Repair the wiring)
- 44. Check for software updates for both ECM and TCM. Are the modules running the latest software version? (Yes: Further diagnose ECM/TCM; No: Update software and retest)
Common causes
- Faulty wiring between the ECM and TCM
- Bad connectors or poor connections
- Faulty ECM or TCM
- Software issues in ECM/TCM
- Corroded grounds or poor battery connections
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Not recommended. You may experience shifting problems that could affect drivability.
Will this code come back?
If the underlying issue isn't fixed, yes, it will likely return.
Why does this code relate to the transmission system?
The ECM and TCM need to work together for proper shifting and engine performance.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
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