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SPN 639 - FMI 9 (Fault Code 285)

SPN639 FMI9
SAE J1939 Multiplexing PGN Timeout Error - Abnormal Update Rate

SAE J1939 Datalink Circuit


CODES:
Fault Code: 285
PID(P), SID(S): S231
SPN: 639
FMI: 9/9
Lamp: Amber

REASON: The ECM expected information from a multiplexed device but did not receive it soon enough or did not receive it at all.

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 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 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 Codes:
-The Engine Control Module (ECM) did not receive a message from a multiplexed device.
-The Engine Control Module (ECM) detected 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 and/or the malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails. The multiplexed device will not operate.

Conditions for Clearing the Fault Code:
• To validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.
• The fault code status displayed by the recommended Cummins® electronic service tool or equivalent will change to INACTIVE immediately after the diagnostic runs and passes.
• The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
• The “Reset All Faults” command in the recommended Cummins® electronic service tool or equivalent 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 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 the recommended Cummins® electronic service tool or equivalent to monitor multiplexed components.

-It is possible to use the recommended Cummins® electronic service tool or equivalent to monitor multiplexed components.
• Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.


Read More:
SPN 441 - FMI 3 (Fault Code 293)
SPN 639 - FMI 13 (Fault Code 286)









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