Cummins X15 CM2350 X116B Performance Series (2018 & Newer) Fault Code: 3838 PID: SPN: 2978 FMI: 9/9 Estimated Engine Parasitic Losses – Percent Torque – Abnormal Update Rate

Lamp:
Amber

Reason:
A loss of communication has been detected.

Effect:
None on performance.

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 (VECU) or transmission Electronic Control Unit (ECU) 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 OEM ECM over the SAE J1939 data link. Messages sent from OEM VECUs or transmission ECUs are received by the OEM ECM and used for controlling the engine. The OEM ECM and OEM VECUs must be configured properly so that proper operation of the multiplexed components will occur.

Component Location:
The SAE J1939 data link wiring and the 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 Code:
The Engine Control Module (ECM) detected a loss of communication with the OEM VECU.

Action Taken When the Fault Code is Active:
The ECM illuminates the amber check engine lamp immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code:
1. To validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.
2. The fault code status displayed by the recommended diagnostic tool or equivalent will change to inactive immediately after the diagnostic runs and passes.
3. The ECM will turn off the amber check engine lamp immediately after the diagnostic runs and passes.
4. The “reset all faults” command in the recommended diagnostic tool or equivalent can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop Talk:
Possible causes of this fault code include:
1. A malfunctioning SAE J1939 datalink circuit.
2. Incorrect feature and parameter settings.