Engine Control Module (ECM) Power Supply Negative Voltage Detected
The ECM has detected a negative voltage on its 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 computer that runs the engine is seeing a voltage drop to below 0 volts on its power supply, which can cause it to malfunction or shut down.
What the computer is actually seeing
The ECM constantly monitors its power supply voltage. If the voltage drops below a defined threshold (usually around -0.5V to 0V), it triggers this fault code indicating a serious issue with the power supply circuit.
What a healthy reading looks like
ECM power supply voltage should be between 10V and 16V during operation.
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; it should be 12.4V or higher with the engine off.
- 22. Inspect the wiring and connectors for any visible damage or corrosion; repair as necessary.
- 33. Use a multimeter to measure voltage at the ECM power supply pin; it should read between 10V and 16V.
- 44. If voltage is below 10V, trace the power circuit back to the battery to identify shorts or opens.
- 55. If voltage is correct, consider swapping the ECM with a known-good unit to eliminate it as a source of the problem.
Common causes
- Damaged wiring or connectors in the power circuit to the ECM
- Short circuit in the ECM power supply circuit
- Defective ECM
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
No, this code can cause the engine to stall or not start, so it’s not safe to drive.
Will this fault come back after clearing?
If the underlying issue isn't fixed, yes, it will likely return.
Why does this code sometimes pair with other SPN codes?
Other codes may indicate related electrical issues or faults within the ECM affecting its operation.
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