P0563 Code: System Voltage High
The engine computer sees too much supply voltage – usually an overcharging alternator cooking the battery.
Safety first · Consult a professional
- Fire risk: stop driving if you smell burning or see smoke.
At a glance
Severity: Moderate
- Meaning
- System Voltage High
- System
- Speed & Idle Control · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $80–$900
- DIY difficulty
- Moderate
P0563 sets when the PCM measures supply voltage above a manufacturer threshold, typically somewhere around 15.5–16 volts, for longer than a set time. A healthy charging system rarely goes much above 14.8 volts, although some smart-charging systems briefly run about 15 volts in cold weather to recharge an AGM battery. Sustained overvoltage almost always means the alternator's voltage regulator has lost control, or the PCM or battery sensor that commands the alternator is getting bad information. It can also be set by jump-starting from a running vehicle with a higher-voltage system or by a battery charger or booster left in 'boost' mode while the engine runs. Unlike low voltage, too much voltage does real harm: it boils the battery, shortens bulb life and can damage control modules.
Can I keep driving? Drive only as far as necessary and switch off the engine if you smell rotten eggs or see the battery steaming. Turn on the headlights and blower to absorb some of the excess, and have the charging system tested right away.
How to read P0563
- P Powertrain
- 0 Generic (SAE)
- 5 Speed, idle & inputs
- 63 Specific fault
Symptoms
- Voltmeter or scan tool showing 15.5 V or more at the battery
- Headlights noticeably brighter than usual and bulbs burning out often
- Rotten-egg (sulfur) smell, hot or swollen battery, acid around the vent caps
- Battery, ABS or traction lights and other warning messages coming on
- Some modules shutting down loads or entering a protective mode
- Code set right after a jump start or charger use
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Failed internal voltage regulator in the alternator
- Fault in the PCM-controlled charging command or battery current/temperature sensor
- Open battery sense wire or poor alternator/regulator ground
- Jump starter, booster pack or charger connected with the engine running
- Worn battery with high internal resistance causing voltage spikes
- PCM misreading its own supply voltage
- Aftermarket voltage booster or incorrectly wired accessory
Diagnosis step by step
Measure at the battery with the engine running
At about 2,000 rpm, a normal system shows roughly 13.5–14.8 V; around 15 V for a short time on a cold morning can be normal with smart charging. A steady reading above about 15.5 V that rises further with rpm confirms overcharging.
Tools: Multimeter
Check the battery for heat and gassing
Carefully feel the battery case and look for bulging sides, electrolyte around the caps or a sulfur smell. A battery in this state releases explosive hydrogen, so keep sparks and flames away and don't load-test or jump it until it has cooled.
Tools: Gloves, Flashlight
Compare commanded and actual charging voltage
On vehicles with PCM-controlled charging, read the generator command (desired voltage or duty cycle) on the scan tool. If the PCM is asking for normal voltage but the battery sees much more, the alternator's regulator is not following the command.
Tools: OBD-II scanner, Multimeter
Check sense wire and grounds
Measure voltage drop between the alternator case and battery negative with loads on; more than about 0.2 V can make the regulator overcompensate. On alternators with a separate battery sense wire, check that it has full battery voltage.
Tools: Multimeter
Inspect the battery sensor
Many newer vehicles have a sensor on the negative battery cable that reports charge and temperature to the PCM. A damaged sensor, a loose connector or a ground cable routed incorrectly after a battery swap can make the system overcharge.
Tools: Flashlight, OBD-II scanner
Rule out external sources
Ask whether the car was jump-started or connected to a charger when the code set. If so, clear it and recheck; if the code doesn't return and charging voltage is normal, no repair is needed.
Tools: OBD-II scanner
Where the parts are
- 1Battery
- 2Alternator
- 3Engine computer (ECM)
- 4CAN bus
- 5Transmission
- 6Wheel speed sensor
- 7High-voltage battery
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Replace voltage regulator (where serviceable separately) | No | $100–$300 |
| Replace alternator | No | $400–$900 |
| Replace battery current/temperature sensor | No | $100–$300 |
| Repair sense wire or alternator ground | No | $80–$250 |
| Replace overcharged battery | Yes | $150–$400 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Emissions / smog test impact
Depends
Whether P0563 turns on the check engine light depends on the vehicle; if it does, the car fails an OBD-II emissions test. More importantly, overcharging can destroy the battery and modules, so fix it before the test regardless.
Frequently asked questions
Can overvoltage really damage my car's electronics?
Yes. Modules are designed to tolerate short spikes, but hours at 16 volts or more stress their power supplies and can kill bulbs, the battery and in bad cases a control module. That is why this code deserves quicker action than a low-voltage code.
My new battery smells and got hot. Is the battery faulty?
Usually the battery is the victim, not the cause. An overcharging alternator forces current into a full battery until the electrolyte boils. Replacing the battery without fixing the charging system will ruin the next one too.
Is 15 volts always a problem?
Not always. Some vehicles with smart charging and AGM batteries raise charging voltage to about 15 volts for a short time when cold. Voltage that stays above about 15.5 volts once the engine is warm is not normal.
Could jump-starting another car have caused this?
It can, especially if the other vehicle's system was higher voltage or a booster pack was left connected while your engine ran. Clear the code; if charging voltage is normal and the code doesn't return, it was a one-off.