Circuit DescriptionThe adaptive cruise control system sends commands to the ECM via the J1939 data link to limit engine speed and maintain a set following distance behind a vehicle travelling more slowly than the current cruise control set speed.

Component LocationThe SAE J1939 data link wiring and the SAE J1939 devices vary by OEM options.

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 did not receive a message from the multiplexed device.

Action Taken When the Fault Code is ActiveThe ECM logs the fault code immediately when the diagnostic runs and fails.The adaptive cruise control will not operate.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 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 TalkIf Adaptive Cruise Recovery is enabled, the driver can toggle the cruise enable switch from the OFF position to the ON position two times to get regular cruise control to operate and Fault Code 784 will go inactive. At the next key cycle, if the Heartbeat message is still not present, Fault Code 784 will go active.

Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

Possible Cause:1) ECM calibration