Power Supply Circuit Low Voltage
The transmission control module (TCM) has detected low voltage in the power supply circuit.
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 TCM needs a certain amount of voltage to work properly. If it gets below that, it won't function correctly, and you might have shifting issues.
What the computer is actually seeing
The TCM senses that the voltage on its power supply circuit is dropping below a threshold, usually around 10.5 volts.
What a healthy reading looks like
Voltage should be between 11.5 to 14.5 volts with the engine running and battery voltage should be roughly 12.6 volts at rest.
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 battery voltage with a multimeter. Should be 12.6 volts (engine off) and 13.5 to 14.5 volts (engine running).
- 22. Inspect battery connections for corrosion or loose cables. Fix any issues found.
- 33. Test the alternator output to ensure it is charging the battery properly. Should be around 13.5 to 14.5 volts with engine running.
- 44. Inspect wiring to the TCM for damage, pinched areas, or corrosion. Repair any found issues.
- 55. If all above are good, replace the TCM.
Common causes
- Weak battery or poor battery connections
- Faulty alternator not charging the system
- Damaged wiring in the power circuit to the TCM
- Faulty transmission control module itself
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's best to avoid driving until resolved as shifting may be erratic and lead to further issues.
Will this code come back after clearing it?
If the underlying issue isn't fixed, yes, the code will likely return.
Why does this relate to the battery?
Low voltage in the battery directly affects the TCM's power supply and its ability to control the transmission.
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