CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 429

Water-in-Fuel Indicator Sensor Circuit – Voltage Below Normal, or Shorted to Low Source


Fault Code: 429
PID: P097
SPN: 97
FMI: 4/4
LAMP: Amber

Water-in-Fuel Indicator Sensor Circuit – Voltage Below Normal or Shorted to Low Source. Low voltage detected at the water-in-fuel circuit.

None on performance. No water-in-fuel warning available.

ISX – Water-in-Fuel Sensor Indicator
ISM – Water-in-Fuel Sensor Indicator

Circuit Description

The water-in-fuel sensor is attached to the fuel filter. The electronic control module (ECM) provides a 5 VDC reference signal to the water-in-fuel sensor. When the water collected in the fuel filter covers the sensor probes, the water-in-fuel sensor then pulls the 5 VDC reference voltage to ground indicating high water accumulation in the fuel filter.

Component Location

The water-in-fuel sensor is integrated into the bottom of the OEM supplied suction fuel filter.

Conditions for Running the Diagnostics

This diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault Codes

The ECM detects that the sensor signal voltage is below 0.05 VDC for one second.

Action Taken When the Fault Code is Active

  • The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code

The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.

Shop Talk

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM. Refer to Procedure 019-032 (ECM Calibration Code) in Section 19 in the corresponding Troubleshooting and Repair Manual for the engine being serviced.

Possible causes of this fault code include:

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

Refer to Troubleshooting Fault Code t05-429

Last Modified:  09-Jul-2010