Circuit DescriptionThe engine brake active lamp relay is controlled by the engine control module (ECM). It is energized during engine braking to illuminate the brake lamps at the rear of the vehicle.

Component LocationLocation of the relay is OEM dependent. Refer to the OEM service manual for the relay 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 ECM detects that the engine brake lamp active relay signal circuit has gone below 0.75-VDC for more than 1 second.

Action Taken When the Fault Code is ActiveThe ECM illuminates the amber CHECK ENGINE lamp and/or the malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.Conditions for Clearing the Fault CodeTo validate the repair, 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 after the diagnostic runs and passes.For On-Board Diagnostics (OBD) engines, the ECM will turn off the MIL after three consecutive trips where 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 TalkThe ECM monitors the voltage level on the engine brake lamp active relay circuit. If the voltage goes above a calibratable limit, this fault is recorded.

Possible causes of this fault code include:

? A short circuit to ground in the OEM harness.

? A pin-to-pin short in the OEM harness.

Possible Cause:1) ECM calibration