Cummins ISB4.5 CM2150 Fault Code: 429 PID: 97 SPN: 97 FMI: 4 Water-in-Fuel Indicator Sensor Circuit – Voltage Below Normal or Shorted to Low Source.

Posted by PerDiezel Solutions on January 20, 2026

Circuit Description
The water-in-fuel sensor is attached to the fuel filter. The electronic control module (ECM) provides a 5 volt 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 volt 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 water-in-fuel sensor signal voltage is below 0.05-VDC for 1second.

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
-To validate the repair, start the engine and let it idle for 1 minute.
-The ECM will turn off the amber CHECK ENGINE light and the fault code will go inactive immediately after the diagnostic runs and passes.
-This fault code can also be cleared with INSITE™ electronic service tool.

Possible Causes
-Signal circuit shorted to ground in the harness, sensor, or connector.

Cummins ISB4.5 CM2150 Fault Code: 428 PID: 97 SPN: 97 FMI: 3 Water-in-Fuel Indicator Sensor Circuit – Voltage Above Normal or Shorted to High Source.

Cummins ISB4.5 CM2150 Fault Code: 427 PID: SID 231 SPN: 639 FMI: 9 J1939 Data Link – Abnormal Update Rate.

Cummins ISB4.5 CM2150 Fault Code: 425 PID: 175 SPN: 612 FMI: 2 Engine Oil Temperature – Data Erratic, Intermittent, or Incorrect.

Cummins ISB4.5 CM2150 Fault Code: 418 PID: 97 SPN: 97 FMI: 0 Water-in-Fuel Indicator – Data Valid But Above Normal Operating Range – Least Severe Level.

Cummins ISB4.5 CM2150 Fault Code: 415 PID: 100 SPN: 100 FMI: 1 Engine Oil Rifle Pressure – Data Valid but Below Normal Operating Range – Most Severe Level.

Cummins ISB4.5 CM2150 Fault Code: 386 PID: SID 212 SPN: 3509 FMI: 3 Sensor Supply 1 Circuit – Voltage Above Normal or Shorted to High Source.

WARNING!