Cummins ISX12 CM2250 (2010-12) Fault Code: 285 PID: SID 231 SPN: 639 FMI: 9 SAE J1939 Multiplexing PGN Timeout Error- Abnormal Update Rate

Circuit Description
Normally, 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) 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 VECUs must be configured properly so that proper operation of the multiplexed components will occur.

Component Location
The J1939 data link wiring and VECU location varies by OEM. Refer to the OEM service manual.

Conditions for Running the Diagnostics
This diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault Codes
The ECM does not receive a valid J1939 message from a multiplexed device for more than 1 second.

The ECM detects an open or short circuit condition in the J1939 data link harness.

Action Taken When the Fault Code is Active
The ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.
The ECM will use a default state as an input for the multiplexed device.
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.
The Reset All Faults command in INSITE? electronic service tool can be used to clear active and inactive faults.

Shop Talk
When this fault code is active, some multiplexed devices can possibly not function as desired.

This fault can occur for the following reasons:

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. This can be caused when a multiplexed component is enabled in the 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 damaged J1939 data link connection between the OEM VECU and Cummins? ECM, a damaged connection between the component and the OEM VECU, damaged OEM VECU or damaged Cummins? ECM. It can become 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) ECM failure