Circuit DescriptionThe adaptive cruise control unit communicates with the electronic control module (ECM) sending and receiving vehicle speed control messages through the SAE J1939 data link.

Component LocationThe location of the adaptive cruise control unit will vary by original equipment manufacturer (OEM). Refer to the OEM service manual.

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

Conditions for Setting the Fault CodesThe ECM does not receive a valid J1939 message from the adaptive cruise control module for more than 1 second.

Action Taken When the Fault Code is ActiveThe ECM will log 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, 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.

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.

For intermittent power supply and datalink communication issues with Aftertreatment Components, it is highly recommended that the OEM Power Distribution Center fuses and relays be thoroughly checked for loose, missing or intermittent connections.

Possible Cause:1) ECM Calibration