Power Supply Voltage Too Low
The ECM has detected a power supply voltage below a normal range.
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 controlling the engine is not getting enough power, which can cause the engine to run poorly or not at all. This usually means that the system voltage is dropping below about 9 volts for too long.
What the computer is actually seeing
The ECM sees a voltage in the power supply line dropping below 9 volts for a specified period, leading to a fault code when it can't maintain normal operations.
What a healthy reading looks like
Normal operating voltage should be between 12.0 to 14.5 volts.
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 battery voltage with a multimeter; should be within 12.0 to 14.5 volts while running. If low, recharge or replace the battery.
- 2Inspect battery terminals and connections for corrosion or looseness; clean and tighten as necessary.
- 3Start the engine and check voltage at the alternator; should output between 13.5 to 14.5 volts. If low, it may need replacement.
- 4Examine wiring and connectors from the battery to the ECM for any damage or signs of wear; repair as necessary.
- 5If all components check out but the code persists, consider ECM replacement.
Common causes
- Bad battery connections
- Weak battery
- Faulty alternator
- Damaged wiring or connectors in the power circuit
- ECM malfunction
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's best to get it checked soon; it might lead to stalling or electrical issues.
Will the code come back if I clear it?
Yes, if the underlying issue isn't fixed, it will likely return.
Why does this code sometimes pair with SPN 100?
Both codes may indicate issues with voltage supply, often related to the same power circuit problems.
Working a real vehicle right now?
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