P0563: System Voltage High
P0563 means the car's computer measured its own supply voltage above the upper limit. It is a moderate concern: the car may still run, but a charging system that is overcharging can damage the battery and electronics.
You can drive, but get it checked soon
The check engine light is not normally on and limp mode is not listed for this code, but high voltage can burn out bulbs and upset other modules. If the charge warning is on or lights flicker, have the charging system tested soon and avoid long trips.
What it means
The engine control module (the car's main computer) constantly measures the voltage it receives from the electrical system. P0563 is stored when that voltage is above its threshold. In GM's engine modules the threshold is 18 V or more in 400 of 500 samples, and one Saab model uses above 18 V for 5 seconds. The code is usually set without turning on the check engine light. Typical triggers are an overcharging regulator (the part that limits how much voltage the alternator makes) or a jump start or charger running at 24 V. Saab's EDC16 diesel reports the same condition as P0560 instead.
Likely causes
- Regulator or alternator overchargingVery likely
A failing regulator can let the alternator push voltage above the limit the computer accepts.
- 24 V jump start or fast chargerPossible
A source at 24 V puts far more voltage into the system than a 12 V car is built for.
- Missing battery or poor battery terminal (voltage spikes)Possible
The battery normally smooths out voltage peaks, so a missing or badly connected one lets spikes through.
- Alternator control line from the module (smart charging)Less likely
On cars where the computer controls the alternator, a fault in that control line can cause overcharging.
What you may notice
- Charge warning light
- Bulbs burning out or lights flickering
- Several modules switching off or reporting faults
What to check, cheapest first
- 1Think back: was the car recently jump-started or charged with a 24 V source or fast charger? Tell the shop if so. · you can do it
- 2Look at the battery terminals and cables for looseness, corrosion, or damage, and confirm the battery is installed and connected. · you can do it
- 3Measure battery voltage with the engine running using a multimeter and compare it with the specification for your car. · you can do it
- 4Read all stored codes, including related ones such as P0560, P0561, P0562, P0620 and P0622. · mechanic
- 5Test the alternator and regulator output under load and check for voltage spikes. · mechanic
- 6On a car with smart charging, check the alternator control line and wiring from the module. · mechanic
Related codes
Frequently asked questions
Can I drive with P0563?+
Short trips are usually possible, but overcharging can damage the battery, bulbs and electronics, so get it tested soon.
Can a gas cap cause P0563?+
No. This code is about electrical system voltage, not the fuel system.
Will P0563 fail an emissions test?+
The code is not emissions-relevant and normally does not turn on the check engine light, but other faults could, so fix the charging problem first.
Written with the help of AI from the public OBDex definition (CC0). Each make may use the code differently. Updated: 2026-11-10