Circuit DescriptionDevices such as ABS controllers, autoshift transmissions, ASR systems, electronic displays, electronic information systems, electronic service tools, and vehicle electronic control unit(s) (VECUs) can communicate with the ECM over the SAE J1939 data link. Messages sent from the devices are received by the ECM and used for controlling the engine. The ECM also transmits information to these devices over the SAE J1939 data link.
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.
Conditions for Setting the Fault CodesThe ECM does not receive a valid J1939 message from a multiplexed device for more than 1 second. The ECM detects an open or short circuit condition in the J1939 data link harness.
Action Taken When the Fault Code is ActiveThe ECM will log the fault code immediately when the diagnostic runs and fails.The ECM will use a default state as an input for the multiplexed device.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 TalkPossible causes of this fault include:
Electrical problems with the SAE J1939 data link wiring such as grounded, shorted, or open circuitsThe ECM (or another SAE J1939 device) tying up communications by sending too many consecutive messagesThe external OEM controlling device has malfunctioned or can no longer transmit on the data link.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