Cummins ISX CM870 (2003-06) Fault Code: 265 PID: P174 SPN: 174 FMI: 4/4 Engine Fuel Temperature Sensor Circuit – Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at engine fuel temperature circuit.

Beginning with 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 engine fuel temperature sensor shares return wires in the engine harness with other sensors. A shorted return can cause multiple fault codes to be active. Before troubleshooting Fault Code 265, check for multiple fault codes.

Possible causes:

1)Signal shorted to ground in the harness or ECM
2)Signal shorted to return or ground in the sensor.

Possible repairs:

1)Replace the engine fuel temperature sensor.
2)Replace the ECM.
3)Replace the engine harness.