What does code P25B9 mean?

Q: What does code P25B9 mean?

Auxiliary Ignition Switch On/Start Position Circuit High. P25B9 is a generic powertrain code indicating that the auxiliary ignition switch on/start position circuit has been detected as high by the control module. The computer monitors the voltage on this circuit and sets the code when the signal exceeds the expected range, typically indicating a short to voltage or an open ground path.

DTC codes / P25xx · Vehicle speed, idle control and auxiliary inputs / P25B9

P25B9Auxiliary Ignition Switch On/Start Position Circuit High

P25B9 is a generic powertrain code indicating that the auxiliary ignition switch on/start position circuit has been detected as high by the control module. The computer monitors the voltage on this circuit and sets the code when the signal exceeds the expected range, typically indicating a short to voltage or an open ground path.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaVehicle speed, idle control and auxiliary inputs

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.