P0563: System Voltage High
The engine computer is seeing system voltage higher than it should be, usually from an overcharging alternator.
What P0563 means
P0563 is the opposite of P0562. The computer has seen system voltage above its upper limit, often around 16 volts, for a set time while the engine runs. RepairPal lists alternator failure, battery failure, wiring issues and computer failure as causes, with alternator and battery replacement as the common repairs. The usual reason is a voltage regulator inside the alternator that has failed and is letting it charge too hard. On many newer cars, the engine computer controls the alternator output, so a bad sense wire, ground or control signal can also cause it. High voltage stresses the battery, which can boil its electrolyte, and can burn out bulbs and damage electronic modules. RepairPal notes that some accessories like the radio may stop working and the engine may even stall. Shops measure charging voltage at the battery and the alternator, check the ground and sense circuits, and test the battery. Fix overcharging quickly to avoid a bigger electrical repair bill.
Common symptoms
- Check engine light or battery light on
- Very bright or flickering headlights
- Bulbs burning out quickly
- Battery smell or swelling from overcharging
- Electrical accessories acting up
Most common causes
- Failed alternator voltage regulator
- Bad battery that can no longer absorb charge
- Poor sense or ground wire to the alternator or computer
- Jump starting or charger connected while running
- Engine computer charging control fault on computer controlled systems
What to check yourself first
With the engine running, measure voltage at the battery. Readings consistently above about 15 volts point to overcharging. Look at the battery for swelling or a rotten egg smell, and check that the battery cables and engine ground are tight.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace alternator | $809-$1,088 | RepairPal lists alternator replacement as a common repair. |
| Replace battery | $456-$493 | If the battery has been damaged by overcharging. |
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | For a bad sense wire or ground that tricks the regulator. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0562 System Voltage Low
- P0606 Control Module Processor
- U0100 Lost Communication With ECM/PCM "A"
- P0700 Transmission Control System (MIL Request)
- P0601 Internal Control Module Memory Check Sum Error