P0563: System Voltage High
What to do
Do not ignore this one. Overcharging destroys batteries and can damage electronic modules, so the repair gets more expensive the longer it runs. If headlights seem unusually bright, bulbs are failing repeatedly, or there is an acrid smell from the battery, stop driving and have it recovered — an overcharged battery can vent hydrogen and is a real hazard.
What this code means
Supply voltage is above the range the module tolerates, which almost always means the alternator's voltage regulator has failed and is no longer limiting output.
This is the more damaging direction. Sustained overvoltage boils the electrolyte out of the battery, shortens the life of every bulb on the vehicle, and can destroy control modules outright — an expensive and entirely avoidable outcome if it is caught early. A battery that is visibly swollen, hot, or smells acrid has been overcharged and is a genuine hazard.
The fault is usually the regulator inside the alternator rather than anything external, but a poor earth between alternator and body can also cause the regulator to sense low and over-compensate, so the earth is worth checking before the unit is replaced.
Likely causes
Start here
- Faulty alternator voltage regulator · moderate
- Faulty alternator · moderate
Less common
- Corroded earth connection · moderate
- Faulty battery temperature sensor · moderate
Rare
- Incorrect aftermarket alternator · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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