Transmission Control Module (TCM) Requested MIL
The Transmission Control Module has a request for the Malfunction Indicator Lamp (MIL) to be activated.
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)
The computer that controls the transmission is asking the dashboard light to turn on, indicating there's a problem that needs attention.
What the computer is actually seeing
The TCM detects issues in the transmission system, usually by monitoring sensor inputs (like vehicle speed, transmission fluid temperature, etc.) and sending a signal when it finds faults.
What a healthy reading looks like
Voltage from the TCM should be between 0.5V and 4.5V when checked at the output; transmission fluid temp should be within 175-220°F under normal conditions.
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.
- 1Check the vehicle speed sensor wiring and connector for damage.
- 2Inspect transmission fluid level and quality; should be clean and at proper level.
- 3Use a scan tool to check for additional codes that might indicate specific sensor failures.
- 4Test the TCM output signal at the connector; it should be in the expected voltage range.
Common causes
- faulty transmission control module
- bad wiring or connectors to the TCM
- sensor failures (speed, temp, etc.)
- transmission fluid level low or dirty
- internal transmission issues
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, but fix it soon as it can affect drivability and performance.
Will the light come back if I clear it?
Yes, if the underlying issue isn't fixed, the light will return.
Why does this code pair with transmission performance issues?
The TCM manages transmission functions; faults can lead to shifting problems or overall poor performance.
Working a real vehicle right now?
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