P0563: System Voltage High (Meaning, Causes, Fixes)
What P0563 means
The charging system (alternator and voltage regulator) keeps the electrical system at the right voltage while the engine runs. On many vehicles the PCM controls the alternator's voltage regulator through a power or ground circuit, and it watches its own ignition feed circuit to see whether charging is working, per OBD-Codes.com. If that voltage is too high, P0563 sets. OBD-Codes.com says a healthy system reads about 13.2 to 14.7 volts at the battery with a load on, and treats anything above 15.5 volts as a charging system problem. The exact trigger point varies by vehicle. Note that RepairPal's description says the code sets when battery voltage drops below 10 volts, which matches the opposite code (P0562, System Voltage Low) rather than a high-voltage code, so we rely on the code's official name and OBD-Codes.com here. P0562 is the matching low-voltage code, and P0560 and P0561 cover system voltage in general and unstable voltage.
Severity: can I keep driving?
Drive with caution, fix soon
Get it checked soon. RepairPal rates P0563 Moderate. OBD-Codes.com gives no severity rating, but lists a transmission that may not shift, stalling and a no-start among the possible symptoms. Charging voltage that stays too high can also be hard on the battery and electronics, so don't ignore it, and if the red battery light is on, have the charging system tested right away. An open code can also fail an OBD2 emissions inspection.
Common symptoms
- Check engine light on (OBD-Codes.com)
- Red battery or charging light on (OBD-Codes.com)
- Transmission may not shift (OBD-Codes.com)
- Engine may not start, or may stall (both sources)
- Some electrical accessories, such as the radio, may not work (RepairPal)
- Lower fuel economy (OBD-Codes.com)
Likely causes
Roughly most to least common, based on the sources below. Your vehicle may differ.
- Faulty alternator or its built-in voltage regulator (OBD-Codes.com calls the alternator the most common cause; RepairPal lists alternator failure first)
- High resistance in the cable between the alternator and the battery (OBD-Codes.com)
- An open or poor connection in the circuit between the alternator and the PCM (OBD-Codes.com); RepairPal lists a wiring issue
- Battery failure (RepairPal)
- Less often, a failed PCM (OBD-Codes.com calls this unlikely; RepairPal also lists PCM failure)
Diagnostic steps you can do
Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.
- Check for technical service bulletins (TSBs) for your vehicle; OBD-Codes.com says this can save time.
- Check the alternator belt and make sure the battery terminals and cables are clean and tight.
- With the engine running, headlights on and the blower fan on high, measure voltage at the battery with a multimeter. OBD-Codes.com says it should be between 13.2 and 14.7 volts; above 15.5 volts points to the charging system, mainly the alternator.
- If you don't have a meter, most auto parts stores will test the battery, starter and charging system for little or no cost, per OBD-Codes.com.
- If voltage is normal, clear the code and see if it returns. If it doesn't, it was likely an intermittent or history code.
- If it returns, inspect the PCM connectors and wiring for corrosion, rubbing, melted plastic or burn marks, and clean the terminals.
Typical fixes
- Replace the alternator (or its voltage regulator, where serviceable) if testing shows it is overcharging; RepairPal lists alternator replacement as a common repair
- Repair or replace high-resistance battery and alternator cables
- Repair wiring or connectors between the alternator and the PCM
- Replace the battery if testing confirms it has failed; RepairPal lists battery replacement as a common repair
- Replace the PCM only after all other tests pass; it must be programmed to the vehicle (OBD-Codes.com)
Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.
🛠 When to call a pro
- Battery voltage reads above about 15.5 volts with the engine running, and you aren't comfortable replacing the alternator
- The voltage looks normal but the code keeps returning; OBD-Codes.com's next steps test the PCM's ignition feed and ground circuits with the harness unplugged and need a wiring diagram
- The car stalls, won't start or won't shift
- A PCM replacement is suspected, since it must be programmed to the vehicle
Where to buy
Plain search links. Always match parts to your exact year, make, model and engine.
FAQs
Is P0563 serious?
RepairPal rates it Moderate, so it isn't usually an emergency, but get it diagnosed soon. OBD-Codes.com lists stalling, a no-start and shifting problems as possible symptoms, and overcharging can be hard on the battery and electronics.
Is P0563 the alternator or the battery?
OBD-Codes.com calls a faulty alternator the most common cause. RepairPal lists both alternator and battery replacement as common repairs. A charging system test (voltage at the battery with the engine running and a load on) tells you which one it is.
What voltage sets P0563?
It depends on the vehicle. OBD-Codes.com says a healthy running system reads about 13.2 to 14.7 volts at the battery under load, and anything above 15.5 volts means the charging system needs diagnosis.
Why do the sources disagree?
RepairPal's description says P0563 sets when battery voltage drops below 10 volts, which describes low voltage (P0562), not the code's official meaning of System Voltage High. OBD-Codes.com's repair steps also mention low battery voltage and a disconnected battery as common causes, wording that matches its P0562 page. Both agree the alternator is the top suspect. RepairPal lists battery failure, which OBD-Codes.com doesn't, and only OBD-Codes.com lists a red battery light, shifting problems and lower fuel economy as symptoms.
Sources
Last reviewed 2026-10-25. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.