Circuit DescriptionNormally, switches, accelerators, and other components are connected to the engine electronic control module (ECM) directly through individual wires. Multiplexing allows those same components to be hard wired to an original equipment manufacturer (OEM) VECU 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 VECU to the Cummins? ECM over the SAE J1939 data link. Messages sent from the OEM VECU or transmission electronic control unit are received by the Cummins? ECM and used for controlling the engine. The Cummins? ECM and OEM VECU must be configured properly so that proper operation of the multiplexed components will occur.

Component LocationThe J1939 data link wiring and VECU location varies by OEM.

Conditions for Running the DiagnosticsThis diagnostic runs continuously when the key switch is in the ON position or when the engine is running.

Conditions for Setting the Fault CodesThe OEM VECU determines that there is a malfunction of the wheel-based vehicle speed sensor.

Action Taken When the Fault Code is ActiveThe ECM illuminates the amber CHECK ENGINE lamp and/or 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 Diagnostic (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 J1939 multiplexing controller has indicated a malfunction of the wheel-based vehicle speed sensor.

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