Cummins ISX CM870 (2003-06) Fault Code: 429 PID: P097 SPN: 97 FMI: 4/4 Water-in-Fuel Indicator Sensor Circuit – Voltage Below Normal or Shorted to Low Source. Low voltage detected at the water-in-fuel circuit.

Beginning with Engine Serial Number (ESN) 14039654, the temperature sensor return circuit was separated from the pressure sensor return circuit. For ESNs prior to this and with engine wiring harness Part Number 3682854, refer to the Common Pressure/Temperature Sensor Return Circuit above. For this ESN and greater or for any other engine wiring harness part number, refer to the Separate Pressure/Temperature Sensor Return Circuit above.

The water-in-fuel sensor shares return wires in the engine harness with other sensors. An open return can cause multiple fault codes to be active. Before troubleshooting Fault Code 429, check for multiple fault codes.

Possible causes:

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

Possible repair:

1)Replace the water-in-fuel sensor.
2)Replace the ECM.
3)Repair or replace the engine harness or sensor extension harness.