Cummins ISB CM850 (2003-06) Fault Code: 429 (Marine) 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.

In automotive, industrial, and power generation applications, 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)Water in fuel
2)Damaged sensor
3)Fuel contamination.

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.