P25B8Auxiliary Ignition Switch On/Start Position Circuit Low
- Generic OBD-II code · Powertrain
- How the car detects it
- P25B8 means the auxiliary On/Start input sits at a low level when the module expects it to be active, or never rises when the remote switch is operated. Typical reasons are a switch contact that no longer closes, a blown fuse feeding the remote panel, a broken wire in the long harness run to the body or a short to ground at a frame connector. In practice it behaves like a dead remote switch: requests from the auxiliary position are ignored, so a crew working at the body or platform cannot start the engine or keep it on from there. As no maker publishes this code, the GM main-switch case serves as reference, where GM's brake control module needs its wake-up line low for 3 s against a run/crank message from the ECM before logging P2534 as a Type B fault. P25B9 covers the opposite direction.
- What you may notice
- Remote start or on request is ignored
- Engine may shut down when the auxiliary position is used to keep it running
- Remote panel indicator stays dark
- Likely causes
- LikelyBlown fuse or failed relay feeding the auxiliary switch
- PossibleSignal wire shorted to ground on the frame or body
- PossibleAuxiliary switch contact no longer closes
- RareCorroded exterior connector with high resistance
- Repair
- Medium · Usually a job for a workshop.Typical cost: €60 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.