Cummins ISX11.9 CM2250 (2010-12) Fault Code: 3641 PID: SID 231 SPN: 748 FMI: 9 Transmission Output Retarder- Abnormal Update Rate

Circuit Description
Normally, switches, accelerators and other components are connected to the electronic 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 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 VECU(s) 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 key swith is in the ON position or when the engine is running.

Conditions for Setting the Fault Codes
The ECM did not receive a message from the multiplexed device.

Action Taken When the Fault Code is Active
The ECM illuminates the amber CHECK ENGINE light and/or the 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 Diagnostic (OBD) engines, the ECM will turn off the MIL after 3 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
When this fault code is active, some multiplexed devices may not function as desired.

This fault can occur for the following reasons:

When the ECM is set up properly (components enabled and OEM Vehicle Control Unit (ECU) 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. This can be caused when a multiplexed component is enabled in the Cummins? ECM, but the OEM VECU source address of the VECU transmitting the component message is incorrect in the Cummins ECM, or the OEM VECU is not set up to transmit the multiplexed component message.
This fault can also be caused by a bad J1939 data link connection between the OEM VECU and Cummins? ECM, a bad connection between the component and the OEM VECU, bad OEM VECU or bad Cummins? ECM. It may be necessary to contact the OEM for proper multiplexing configuration.It is possible to use INSITE? electronic service tool to monitor multiplexed components.
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) OEM harness
2) ECM failure