What does code P256B mean?

Q: What does code P256B mean?

Engine Idle Speed Selector Sensor/Switch Range/Performance. P256B indicates that the powertrain control module (PCM) has detected an out-of-range or performance fault in the engine idle speed selector sensor or switch circuit. This sensor or switch is responsible for reporting the driver's selected idle speed mode, such as a high-idle or fast-idle request, to the PCM, which then adjusts engine idle speed accordingly. The code sets when the PCM sees a signal that does not match expected values for the current operating conditions, often due to a faulty switch, wiring issue, or sensor failure.

DTC codes / P25xx · Vehicle speed, idle control and auxiliary inputs / P256B

P256BEngine Idle Speed Selector Sensor/Switch Range/Performance

P256B indicates that the powertrain control module (PCM) has detected an out-of-range or performance fault in the engine idle speed selector sensor or switch circuit. This sensor or switch is responsible for reporting the driver's selected idle speed mode, such as a high-idle or fast-idle request, to the PCM, which then adjusts engine idle speed accordingly. The code sets when the PCM sees a signal that does not match expected values for the current operating conditions, often due to a faulty switch, wiring issue, or sensor failure.

SystemPowertrain

Code typeGeneric (all makes)

SeverityLow

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.