OBD-II code · Powertrain (generic)
P0561 System Voltage Unstable
The ECU monitors battery voltage and detects unstable behaviour - rapid fluctuations beyond what current load changes explain. Typical causes are a failing alternator, loose battery terminals, weak battery, or a heavy load (radiator fan, glow plugs, heated screen) drawing voltage down briefly.
Is it safe to drive with P0561?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyAlternator regulator failing
- PossibleBattery weak or terminals loose
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.5–3 h
- Emissions test
- Usually unaffected
- Parts involved
- Alternator, Battery, Main Supply Wiring
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.