Cummins X12 CM2350 X119B (2018 & Newer) Fault Code: 6338 PID: SPN: 639 FMI: 13/13 SAE J1939 Multiplexing Configuration Error – Out of Calibration

Lamp:
None

Reason:
The ECM expected information from a multiplexed device but only received a portion of the necessary information.

Effect:
At least one multiplexed device will not operate properly.

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 ECM over the SAE J1939 data link.
Messages sent from OEM VECUs or transmission ECUs are received by the ECM and used for controlling the engine. The 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 Diagnostic:
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 Engine Control Module (ECM) received an invalid J1939 data link message from a multiplexed device for more than 1 second.

Action Taken When the Fault Code is Active:
The ECM illuminates the amber check engine lamp immediately when the diagnostic runs and fails.
The multiplexed device will not operate.

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:
1. This fault can occur when the ECM is set up properly (components enabled and OEM VECU source addressed correctly) to receive information from an OEM VECU, but the OEM VECU is actually transmitting a message that says that component is not available for multiplexing.
2. It is possible to use the recommended diagnostic tool or equivalent to monitor multiplexed components.
3. Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.