Power Supply Voltage High
The engine control module has detected a higher than normal power supply voltage.
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What it means (plain English)
When the engine control module (ECM) sees more voltage than it's built to handle, usually above 16 volts, it throws this code to prevent damage.
What the computer is actually seeing
The ECM monitors the voltage level from the battery or alternator. If it exceeds 16 volts, it triggers the code, indicating potential over-voltage conditions.
What a healthy reading looks like
Voltage should be between 12.6V to 14.5V for proper operation. Anything above 16V is a concern.
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 with a multimeter; it should be between 12.6V and 14.5V. If it's over 16V, proceed to step 2. Decision: Over 16V? Yes - Check alternator output; No - Further diagnosis needed.
- 22. Inspect the alternator for damage or malfunction. Test its output while running; it should not exceed 14.5V. Decision: Normal output? Yes - Check wiring; No - Replace alternator.
- 33. Inspect all battery connections for corrosion or looseness. Tighten and clean if necessary. Decision: Connections secure? Yes - Test wiring; No - Fix connections and retest.
- 44. Test the voltage regulator. It should maintain voltage below 15V. Use a scan tool to monitor voltage readings while running the engine. Decision: Voltage stable? Yes - Consider ECM issues; No - Replace voltage regulator.
Common causes
- Faulty alternator
- Damaged voltage regulator
- Bad battery connections
- Corroded wiring or connectors
- Faulty ECM causing false readings
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's not recommended. Driving with high voltage can damage electrical components.
Will this code come back after reset?
If the underlying cause isn't fixed, yes, it will return.
Why is this related to the alternator?
The alternator regulates voltage; if it's malfunctioning, it can produce excessive voltage.
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