Can high voltage ruin my battery?

Yes. Sustained voltage over 15 volts can boil the electrolyte in a lead-acid battery, permanently damaging it. Check the battery after fixing the alternator.

Is this an immediate breakdown risk?

Not immediately, but the battery can fail quickly from overcharging, which then leaves you stranded. Get it checked within a day or two.

My multimeter shows normal voltage but the code is still there. What now?

The fault may have been intermittent. If the PCM reading matches your multimeter and both show normal, clear the code and monitor it. If it returns, have the alternator load-tested.

Codes › P0563

P0563: The electrical system voltage is running too high

System Voltage High

Moderate severityCan you keep driving?

Drive to a shop soon. Sustained high voltage can damage the battery, PCM, and other sensitive electronics. Do not ignore it.

What it means

P0563 means the PCM detected charging system voltage above a safe threshold, typically above 16 volts. Normal charging is 13.5 to 14.8 volts. When voltage exceeds this, the alternator is overcharging and can boil the battery, damage its cells, and harm voltage-sensitive modules. A failed voltage regulator inside the alternator is the most common cause. On most modern vehicles, the regulator is built into the alternator. On some older vehicles it is a separate external part, which is a cheap fix if that is what is at fault.

Common causes

Failed voltage regulatorMost common cause. On most modern cars it is built into the alternator and requires alternator replacement.
Faulty alternator with internal overcharge conditionThe alternator itself is commanding full output and not backing off.
PCM voltage reference or sensor errorRare. The PCM could be reading voltage incorrectly. Verify with a separate multimeter before assuming overcharge.

What it costs

Voltage regulator (external, older vehicles)$30 to $100
Alternator replacement$300 to $700

Symptoms

Check engine light on
Battery warning light may be on
Burning smell from the battery in severe cases
Bulbs burning out frequently
Electronics behaving erratically

What to do next

Verify the overcharge with a multimeter at the battery terminals while the engine runs. If you see over 15 volts, the alternator or regulator is at fault. Compare to the PCM reading; if they agree, the alternator is the problem. Do not let the car sit running with an overcharging alternator; it will damage the battery and potentially other electronics.

Lewis shows the real-time charging voltage from the ECU so you can verify whether the overcharge is confirmed by the sensor or is a sensor error before spending money. Download Lewis.

Related codes

FAQ

Can high voltage ruin my battery?: Yes. Sustained voltage over 15 volts can boil the electrolyte in a lead-acid battery, permanently damaging it. Check the battery after fixing the alternator.
Is this an immediate breakdown risk?: Not immediately, but the battery can fail quickly from overcharging, which then leaves you stranded. Get it checked within a day or two.
My multimeter shows normal voltage but the code is still there. What now?: The fault may have been intermittent. If the PCM reading matches your multimeter and both show normal, clear the code and monitor it. If it returns, have the alternator load-tested.