Case IH 429 – Engine Control Module (ECM): Water in Fuel Sensor voltage is too low

The control module has sensed a voltage lower than expected on the Water in Fuel (WIF) sensor's signal circuit, or the wire is shorted to a low source (ground), preventing normal operation.

• MX Magnum
• STX Steiger
• MX Magnum series
• TG series
• T8000 series
• Maxxum (100-140)
• Puma (125-230 CVX/CVT)
• JX series
• 8.3L engine
• 9.0L engine
• 15L engine
• Cummins QSB
• Cummins QSC
• Cummins QSL9
• Cummins QSM11
• Cummins QSX15

1. 1

   Drain the fuel filter to check for excessive water accumulation

2. 2

   Visually inspect the WIF sensor and connector for damaged pins, corrosion, water ingress, or contamination

3. 3

   Inspect the wiring harness from the Engine ECU to the WIF sensor for abrasion, damage, or incorrect attachment

4. 4

   Perform a voltage and continuity test on the sensor circuit to check for a short to ground in the harness or sensor

1. 1

   Locate fuel filter assembly

   Turn the key switch OFF and locate the fuel filter/water separator assembly on the engine.

2. 2

   Drain water separator

   Open the drain valve at the bottom of the filter to empty any accumulated water. Close the valve securely (do not over-tighten, as this can damage the internal seal).

3. 3

   Check fault codes

   Turn the key switch ON and use a diagnostic tool (or the in-cab display) to read the fault codes. If Code 429 becomes inactive, clear the code and resume operation.

4. 4

   Inspect and clean WIF sensor harness

   If the code remains active, disconnect the WIF sensor harness. Inspect the pins on both the sensor and the harness side. Clean any corrosion with electrical contact cleaner.

5. 5

   Test wiring harness

   Test the wiring harness for a short to ground. If the harness is damaged, repair or replace the affected wiring section.

6. 6

   Diagnose WIF sensor failure

   If the wiring harness tests good and the voltage supply from the ECM is correct, the WIF sensor itself has failed internally and must be replaced.

7. 7

   Replace WIF sensor

   Unscrew the old WIF sensor from the fuel filter housing, install the new sensor, reconnect the harness, and clear the fault codes to verify the repair.