Case IH F-97-31 - ECU – Engine Control Unit (ECU): Water in fuel detected or water in fuel circuit failure

The system monitors the voltage output from the Water in Fuel (WIF) switch/sensor located at the bottom of the primary fuel filter. When water accumulates in the filter, it bridges the sensor's probes, pulling the reference voltage to ground and closing the electrical circuit. The code is triggered either because water has successfully completed this circuit (water detected) or because there is a circuit failure, such as the sensor wiring being shorted to a high voltage source.

• MAGNUM AFS Connect
• 240 Series Combines (7240, 8240, 9240)
• 8010 Series Combines
• Magnum series (MX210, MX230, MX255, MX285)
• Steiger series (Tier 4a and newer)
• Maxxum series
• Puma series
• Farmall compact tractors (40, 45, 50, 35C, 40C, 50C)
• Austoft 9900 sugarcane harvesters

1. 1

   Check if the tractor's battery has been connected to an external power supply (like a jump box or charger). If connected, disconnect it and test for normal operation, as abnormal voltage can trigger this code erroneously.

2. 2

   Visually inspect the Water in Fuel switch (black connector housing) and wiring harness for chafing, pinched wires, or corrosion that could cause a short circuit.

3. 3

   Drain the primary fuel filter/water separator into a clear container to see if water or algae is actually present in the fuel system (actual water contamination cause).

4. 4

   Unplug the sensor to isolate it. If the monitor still throws a constant alarm/code for a shorted circuit while unplugged, the issue is likely in the wiring harness. If the code changes or stops, the sensor itself has likely failed internally.

1. 1

   Preparation

   Safely shut down the machine and locate the primary fuel filter / water separator assembly on the engine.

2. 2

   Drain contaminants

   Open the drain valve at the bottom of the fuel filter to drain any accumulated water. Close the valve, prime the fuel system, and turn the key on to see if the code clears (addresses actual water in fuel cause).

3. 3

   Disconnect sensor

   If the code persists, disconnect the electrical connector from the Water in Fuel sensor at the bottom of the filter housing.

4. 4

   Inspect connector

   Check the pins on both the sensor and the harness side for moisture, corrosion, or damage. Clean with electrical contact cleaner if necessary (addresses wiring/short cause).

5. 5

   Replace sensor and filter

   If the wiring is intact and no water is present in the fuel, the sensor has failed internally. Unscrew the faulty Water in Fuel sensor from the filter housing. It is highly recommended to replace the primary fuel filter at the same time to ensure no residual algae or contamination fouls the new sensor.

6. 6

   Reassembly

   Thread the new Water in Fuel sensor into the new filter, install the filter, and reconnect the wiring harness.

7. 7

   Final test

   Prime the fuel system to remove air, start the engine, and verify that the F-97-31 code is cleared from the display.