Transmission Control Module (TCM) Supply Voltage Out of Range
The Transmission Control Module (TCM) is detecting a voltage issue with its power supply.
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 isn't getting the right voltage, which could lead to incorrect shifting or even stalling.
What the computer is actually seeing
The TCM reports a supply voltage that is outside the normal expected range, typically below 10V or above 16V when the vehicle is running.
What a healthy reading looks like
Normal TCM operation requires a voltage supply between 12V and 14.5V.
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 battery voltage; should be between 12.4V to 12.8V with the engine off. If below, charge or replace the battery.
- 22. With the engine running, measure voltage at the TCM connector; it should be 12V to 14.5V. If voltage is out of range, check for a faulty alternator or broken wiring.
- 33. Inspect the TCM connector for corrosion or loose connections. Repair or replace as necessary.
- 44. Verify the ground connection to the TCM; should read close to 0V when tested to the battery negative. Fix any bad grounds.
- 55. If all wiring and connections are good, consider replacing the TCM.
Common causes
- Corroded or damaged wiring in TCM harness.
- Poor ground connection to TCM.
- Battery voltage issues or bad alternator.
- Faulty TCM itself.
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
No, it may result in erratic shifting or loss of transmission function.
Will the code come back after clearing?
If the underlying issue isn’t resolved, yes, it will return.
Why do I see this code with other SPNs?
This code can indicate broader electrical issues that affect several systems, often appearing with other voltage-related codes.
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