Cummins ISX12 CM2250 (2010-12) Fault Code: 3838 PID: SPN: 2978 FMI: 9 Estimated Engine Parasitic Losses- Percent Torque- Abnormal Update Rate

Circuit Description
Normally, switches, accelerators, and other components are connected to the ECM directly through individual wires. Multiplexing allows those same components to be hard-wired to an OEM VECU or transmission electronic control unit (ECU) in the cab. Component values and states from components such as sensors, accelerators, and switches can then be transmitted from the OEM VECU to the Cummins? ECM over the SAE J1939 data link.

Messages sent from OEM VECUs or transmission ECUs are received by the Cummins? ECM and used for controlling the engine. The Cummins? ECM and OEM VECUs must be configured properly so that proper operation of the multiplexed components will occur.

Component Location
Location of the relay is OEM dependent. Refer to the OEM service manual for the relay location.

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 OEM VECU determines there is a malfunction of the multiplexed accelerator pedal or lever sensor system.

Action Taken When the Fault Code is Active
The 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 Code
To 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 Diagnostics (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 Talk
The J1939 multiplexing controller has detected that a message was not received when it was expected.

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

For intermittent power supply and data link 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