P0561System Voltage Unstable
- Generic OBD-II code · Powertrain
- How the car detects it
- The module measures its own supply voltage. CARB allows other monitors to be suspended below 11 V, and above a maker's threshold only if the voltage itself is diagnosed – that is what these codes record. GM's engine modules and Ford's PCM set them without warning lamp. GM interprets P0561 as a difference between the module's two supply inputs: permanent battery and switched ignition supply may differ by at most 3 V, otherwise it sets after 50 of 63 samples. In the engine module that is type C without warning lamp, in GM's 9-speed transmission module type A with the lamp after one trip. Other makers use it for a fluctuating voltage.
- What you may notice
- Further voltage or communication codes
- Transmission warning or check engine light (GM transmission module)
- Sporadic dropouts of electrical functions
- Likely causes
- LikelyFuse, relay or line of the ignition supply (voltage drop)
- PossibleLoose or corroded connector or ground at the module
- PossibleVoltage regulator fluctuating
- PossibleBattery terminal loose
- Repair
- Medium · Often possible to do yourself.Typical cost: €0 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.