Engine Control Module Power Supply Voltage
Indicates low voltage detected at the engine control module.
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 engine control module (ECM) isn't getting enough power, which can cause the engine to run poorly or not start.
What the computer is actually seeing
The ECM monitors its supply voltage continuously and triggers a fault when it drops below a specified threshold, generally around 9 volts.
What a healthy reading looks like
Expected voltage should be between 12.5 and 14.5 volts at the ECM with the engine running.
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. Should be at least 12.5 volts with the engine off and between 13.5 to 14.5 volts with the engine running. If not, charge or replace the battery.
- 22. Inspect battery connections for corrosion. Clean and tighten if necessary. Check cable integrity for breaks or fraying.
- 33. Verify alternator operation: run the engine and recheck voltage at the battery and ECM. Should be 13.5 to 14.5 volts. If low, test or replace the alternator.
- 44. Check wiring and connectors between the battery, alternator, and ECM for damage or disconnections. Repair any faults found.
- 55. If voltage is normal and connections are good but the code persists, consider testing or replacing the ECM. Before replacing, confirm that power and ground signals to the ECM are good.
Common causes
- Weak battery
- Bad alternator
- Corroded battery connections
- Wiring issues to the ECM
- Faulty ECM
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Moderate severity; driving can cause further engine issues. Fix soon.
Will this code clear on its own?
Not likely; it will stay until you fix the issue or clear it with a scan tool.
Why does this code appear with others like SPN 1602?
They often indicate related power supply issues affecting the ECM.
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