System Voltage Low
This code doesn't point at an engine part: it means the voltage reaching a control unit is too low. It serves as a warning that other codes stored at the same time may be caused by the lack of voltage.
What the car has detected
The control unit has measured a supply voltage below the minimum (for example around 10 volts) for some time with the engine running.
If the battery isn't charging properly, the car can run out of power and stop or fail to start. If it appears once in cold weather, it may just be a weak battery, but get it checked soon.
Symptoms
- Engine or battery warning light on
- Slow or hard starting
- Lights dimming
- Other electrical codes or warnings at the same time
Possible causes
- Weak or ageing battery, especially in cold weather
- Alternator undercharging or a faulty regulator
- Loose or corroded battery terminals, or a poor earth point
- Poor connection in the wiring or connector of the affected control unit
Checks for the garage
- Load-test the battery and measure charging voltage with the engine running
- Check terminals, main cables and earth points
- See whether the same code is in several control units: if so, the cause is shared (battery, alternator or earth)
- If it is only in one control unit, check its supply, earth and connector
- Clear the codes and check they don't come back
Next step
Have the battery load-tested, the alternator charging voltage measured, and the terminals and earth points checked.
Go to a garage if the battery is new and the code comes back, or if the battery light comes on with the engine running. Battery and alternator tests need specific equipment.