System Voltage High
What does P0563 mean?
The P0563 code means the vehicle's onboard diagnostic system has detected: System Voltage High. This is a moderate severity code.
Common Symptoms
- Bulbs burning out frequently
- Battery overheating or bulging
- Electrical components failing prematurely
- Strong sulfur or rotten egg smell from battery
- Check engine light on
Probable Causes (Ranked by Likelihood)
- Faulty voltage regulator (overcharging) Very High
- Failing alternator with internal regulator issue High
- Poor ground connection to alternator or PCM Moderate
- Incorrect alternator installed (wrong output spec) Moderate
- PCM voltage sensing circuit error Low
Step-by-Step Diagnostic Procedure
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Measure charging voltage with engine running -- should be 13.5-14.5V; over 15V indicates overcharging
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Test voltage at different RPMs -- should remain under 14.8V even at 3000 RPM
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Check alternator ground connection for corrosion or looseness
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Inspect battery for signs of overcharging -- swollen case, excessive bubbling, or electrolyte loss
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If voltage is over 15V, replace alternator or external voltage regulator as applicable
Frequently Asked Questions
Can I drive with code P0563?
Only for short distances to a repair shop. High system voltage (overcharging) can damage the battery, blow light bulbs, and fry sensitive electronic components including the PCM, radio, and instrument cluster. The longer you drive, the more damage can occur.
What voltage is too high for a car?
Normal charging voltage is 13.5-14.5V. Anything consistently above 15V is considered overcharging and is harmful. At 16V or higher, battery damage, bulb failures, and electronic component damage occur rapidly.
Can overcharging damage my battery?
Yes. Overcharging causes the battery electrolyte to boil, which can warp the battery case, corrode the terminals, release hydrogen gas (explosive), and permanently damage the battery plates. A swollen battery case is a clear sign of overcharging.