Circuit DescriptionThe brake lamp relay is an OEM optional component used to illuminate the vehicle’s brake lamps under conditions when the engine is braking.

Component LocationThe brake lamp relay is an OEM component. Refer to the OEM service manual for component location.

Conditions for Running the DiagnosticsThis diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.

Conditions for Setting the Fault CodesThe Engine Control Module (ECM) detected the brake lamp relay driver circuit was shorted to high source or open circuit.

Action Taken When the Fault Code is ActiveThe ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.Conditions for Clearing the Fault CodeTo validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop TalkPossible causes of this fault code include:

Incorrect feature and parameter settingsAn open circuit in the OEM harnessA short circuit to battery in the OEM harness

Possible Cause:1) Engine Brake lamp Relay failure2) ECM calibration