Cummins ISB CM850 (2003-06) Fault Code: 429 (Auto) PID: 97 SPN: 97 FMI: 4 Water-in-Fuel Indicator Sensor Circuit – Voltage Below Normal or Shorted to Low Source. Low voltage detected at the water-in-fuel circuit.

Cummins ISB CM850 (2003-06) Fault Code: 429 (Auto) PID: 97 SPN: 97 FMI: 4 Water-in-Fuel Indicator Sensor Circuit – Voltage Below Normal or Shorted to Low Source. Low voltage detected at the water-in-fuel circuit.

The water-in-fuel sensor is integrated into the fuel filter; it is automatically replaced whenever the fuel filter is replaced. For marine applications the sensor is not integrated into the fuel filter and is a serviceable item.

Possible causes:

1)Signal circuit shorted to ground in the harness, sensor, or connector.

Possible repairs:

1)Flush the dirt, debris, or moisture from the connector pins.
2)Install the appropriate connector seal if it is damaged or missing.
3)Replace the water-in-fuel sensor.
4)Replace the ECM.
5)Repair or replace the damaged engine harness.