System Voltage High
What it means
The engine computer has detected supply voltage above the maximum allowed. This usually means the alternator is overcharging because of a voltage regulator fault, which can damage the battery and electronics if it continues.
Symptoms4
- Battery light or check engine light on.
- Lights brighter than usual or bulbs burning out often.
- Acid smell, or a swollen or hot battery.
- Scattered faults in electronic devices.
Possible causes5
- Faulty alternator voltage regulator causing overcharging.
- Fault in the computer's alternator control circuit on vehicles where the computer controls charging.
- Poor alternator sense wire or ground making it read lower than actual voltage and charge harder.
- Use of an external charger or jump starter with high voltage.
- Faulty battery sensor on vehicles that have one.
How to diagnose5
- Measure battery voltage with the engine running and compare it with the manufacturer charging specification.
- Check whether the vehicle was recently connected to a charger or jump starter.
- Inspect the alternator and engine ground points and the sense wire.
- Check for alternator control codes such as P0620 and P0622.
- Inspect the battery for swelling or heat.
How to fix5
- Repair ground points or the sense wire if they have resistance.
- Repair the alternator control circuit if proven faulty.
- Replace the alternator or voltage regulator if charging is too high.
- Replace the battery if it is swollen or damaged by overcharging.
- Clear the codes and confirm charging voltage is within specification.
Repair cost
In Saudi riyals; the highlighted part is the expected range for this fault.
The cost is low when a poor ground or wire is the cause, and rises when the alternator is replaced, more so if the battery was damaged too.
Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026
Frequently asked questions
Is overcharging dangerous?
Yes, if it continues. It can boil and ruin the battery, and raises voltage on electronic modules and bulbs, shortening their life.
The code appeared after a jump start. Is that normal?
It can set briefly if the external source had high voltage. Clear the code and measure charging voltage; if it is correct and the code does not return, there is no problem.
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What was wrong? (optional)
This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.
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