Power Supply Voltage Fault
The engine control module has detected an abnormal voltage condition.
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 unit (ECU) is not getting the proper voltage it needs to operate, usually between 9-16 volts. If it's too low or too high, it can cause issues with engine performance and functionality.
What the computer is actually seeing
The ECU monitors its supply voltage. If the voltage is outside the specified range (9 to 16 volts for most systems), it triggers SPN 1364.
What a healthy reading looks like
Supply voltage should be between 9 and 16 volts while the engine is 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 battery voltage under load. It should be between 12.4V and 12.8V.
- 22. Inspect the main power supply wiring and connectors for damage or corrosion.
- 33. Check alternator output at idle and full load; it should be between 13.5V and 14.5V. Replace if out of range.
- 44. Check all ground connections for continuity and cleanliness; typically should be less than 1 ohm of resistance.
- 55. If all previous checks are good, test/reprogram the ECU for faults.
Common causes
- Faulty alternator
- Weak battery
- Corroded or damaged wiring
- Poor ground connection
- Faulty ECU
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this fault code?
It can be, but may lead to erratic engine performance; it's best to diagnose and fix it soon.
Will the code come back after resetting?
If the underlying issue isn’t resolved, the code will likely return.
Why does this code pair with low battery voltage?
Low battery voltage can cause the ECU’s voltage supply to drop, triggering this fault.
Working a real vehicle right now?
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