Cummins ISM CM875 (2003-06) Fault Code: 426 PID: S231 SPN: 639 FMI: 2/2 Communication between the electronic control module (ECM) and another device on the SAE J1939 data link has been lost.

This fault occurs whenever the ECM starts communicating with any other device using the SAE J1939 data link and then can no longer transmit on the data link.

Possible causes:

1)Electrical problems with the SAE J1939 data link wiring such as grounded, shorted, or open circuits
2)The ECM (or another SAE J1939 device) tying up communications by sending too many consecutive messages.

Possible repairs:

1)Clean the connector and pins.

2)Repair the damaged harness connector or pins, if possible.