Cummins ISB CM850 (2003-06) Fault Code: 497 PID: SID 114 SPN: 1137 FMI: 2 Multiple Unit Synchronization Switch – Data Erratic, Intermittent, or Incorrect. Multi-Unit synchronous ON/OFF switch and Multi-Unit synchronous complimentary ON/OFF switch have different values in the ECM.

The multi-unit synchronization feature allows two or more engines to be controlled by a single throttle signal and run at a similar speed. There is three engine configurations available with this feature: soft-coupled, hard-coupled, and soft-coupled marine.

The soft-coupled configuration has all secondary engines in parallel with each other. The primary engine outputs a throttle signal to all secondary engines. This setup allows all engines to remain running if a secondary engine stops

The hard-coupled configuration has the primary and all secondary engines in series with each other. The primary engine outputs a throttle signal, which is received by the first secondary engine. This secondary engine then outputs the throttle signal the next secondary engine in the series. This process repeats until the primary engine receives the throttle signal.

The soft-coupled mare configuration has all secondary engines in parallel with each other. The primary engine outputs a throttle signal on the J1939 datalink to all secondary engines.

Possible repairs:

1)Replace the multi-unit synchronization switch or the multi-unit synchronization complementary switch.
2)Repair or replace the OEM harness.
3)The removal and reinstallation of the connector may correct the fault.