What does code P05F4 mean?

Q: What does code P05F4 mean?

Exhaust Aftertreatment Power Relay Control Circuit Low. P05F4 indicates that the powertrain control module (PCM) has detected a low-voltage condition on the control circuit for the exhaust aftertreatment power relay. This relay supplies battery power to the aftertreatment system's heater, pump, or control module, and a low circuit means the PCM sees voltage below the expected threshold when the relay is commanded on.

DTC codes / P05xx · Vehicle speed, idle control and auxiliary inputs / P05F4

P05F4Exhaust Aftertreatment Power Relay Control Circuit Low

P05F4 indicates that the powertrain control module (PCM) has detected a low-voltage condition on the control circuit for the exhaust aftertreatment power relay. This relay supplies battery power to the aftertreatment system's heater, pump, or control module, and a low circuit means the PCM sees voltage below the expected threshold when the relay is commanded on.

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.