Circuit Description
Normally, switches, accelerators, and other components are connected to the engine control module (ECM) directly through individual wires. Multiplexing allows those same components to be hard wired to an original equipment manufacturer (OEM) vehicle electronic control unit or transmission electronic control unit in the cab. Then component values and states from components such as sensors, accelerators, and switches can be transmitted from the OEM vehicle engine control unit to the Cummins® ECM over the SAE J1939 data link.
Component Location
The SAE J1939 data link wiring and SAE J1939 devices vary by OEM options.
Conditions for Running the Diagnostics
This diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.
Conditions for Setting the Fault Codes
The ECM detects a loss of communication with the Engine Wait to Start Lamp.
Action Taken When the Fault Code is Active
-The 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 Code
-To validate the repair, perform a key cycle, start the engine, and let it idle for 1 minute.
-The fault code status displayed by INSITEâ„¢ 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.
-For On-Board Diagnostics (OBD) engines, the ECM will extinguish the MIL after three consecutive trips where the diagnostic runs and passes.
-The “Reset All Faults” command in INSITEâ„¢ electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.
Possible Causes
-Incorrect terminating resistance of the SAE J1939 data link circuit
-Incorrect feature and parameter settings
-A malfunctioning SAE J1939 data link circuit.
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