Cummins ISB CM850 (2003-06) Fault Code: 497 PID: SID 114 SPN: 1137 FMI: 2 Multiple Unit Synchronization Switch – Data Erratic, Intermittent, or Incorrect.

Posted by PerDiezel Solutions on January 18, 2026

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.

Cummins ISB CM850 (2003-06) Fault Code: 488 PID: 105 SPN: 105 FMI: 0 Intake Manifold 1 Temperature – Data Valid but Above Normal Operational Range – Moderately Severe Level. Intake manifold air temperature signal indicates intake manifold air temperature above engine protection warning limit.

Cummins ISB CM850 (2003-06) Fault Code: 471 PID: 98 SPN: 98 FMI: 17 Engine Oil Level ? Data Valid But Below Normal Operational Range ? Least Severe Level. Low oil level has been detected by the oil level sensor.

Cummins ISB CM850 (2003-06) Fault Code: 452 PID: 157 SPN: 157 FMI: 4 Injector Metering Rail Number 1 Pressure Sensor Circuit – Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at the rail fuel pressure sensor circuit.

Cummins ISB CM850 (2003-06) Fault Code: 451 PID: 157 SPN: 157 FMI: 3 Injector Metering Rail Number 1 Pressure Sensor Circuit – Voltage Above Normal or Shorted to High Source. High signal voltage detected at rail fuel pressure sensor circuit.

Cummins ISB CM850 (2003-06) Fault Code: 449 (ISC – Auto) PID: 94 SPN: 157 FMI: 0 Injector Metering Rail Number 1 Pressure – Data Valid But Above Normal Operating Range – Most Severe Level. Fuel pressure signal indicates that fuel pressure has exceeded the maximum limit for the given engine rating.

Cummins ISB CM850 (2003-06) Fault Code: 449 (Auto) PID: 94 SPN: 157 FMI: 0 Injector Metering Rail Number 1 Pressure – Data Valid But Above Normal Operating Range – Most Severe Level. The ECM has detected that fuel pressure in the rail fuel is higher than the commanded pressure.

WARNING!