Case IH F-174-01 - ECU – Engine Control Unit (ECU): Fuel temperature sensor voltage is lower than expected

The control module is receiving a voltage signal from the fuel temperature sensor that falls below the minimum acceptable threshold. This condition typically points to a short to ground in the sensor circuit, a damaged wiring harness, or an internally failed sensor.

• MAGNUM AFS Connect
• Puma
• Maxxum
• Farmall
• MXU

1. 1

   Inspect the fuel temperature sensor wiring harness for visible damage, chafing against engine components, or a short to ground.

2. 2

   Disconnect the electrical connector at the fuel temperature sensor and check for diesel fuel contamination inside the plug, moisture, corrosion, or loose/backed-out pins.

3. 3

   With the key in the ON position (engine off), use a multimeter to check the reference voltage at the sensor connector to verify the ECU is sending the correct signal.

4. 4

   Use a diagnostic tool (such as the Case IH Electronic Service Tool or Jaltest) to read live data and confirm the sensor voltage reading. If the voltage remains low when the sensor is unplugged, the issue is likely a short in the wiring harness rather than the sensor itself.

1. 1

   Preparation

   Turn off the engine and allow it to cool. Clean the area around the fuel temperature sensor (typically located on the fuel filter base, fuel rail, or injection pump housing) to prevent dirt from entering the fuel system.

2. 2

   Drain/Isolate Fuel

   Place a clean container under the sensor area to catch spilled diesel. If equipped, close the fuel shut-off valve or pinch the fuel return line to minimize fuel loss.

3. 3

   Disconnect

   Unplug the 2-pin electrical connector from the sensor.

4. 4

   Removal

   Use a wrench (typically a 19mm hex) to unscrew and remove the old fuel temperature sensor.

5. 5

   Installation

   Inspect and clean the port threads. Install the new fuel temperature sensor. (Apply appropriate thread sealant if it is not pre-applied to the new sensor).

6. 6

   Torque

   Tighten the sensor to the manufacturer's recommended torque specification (e.g., 20 ± 3 N·m or approx. 14.7 lb-ft, depending on the exact engine block/filter base).

7. 7

   Reassembly

   Reconnect the electrical connector securely. Open any closed fuel valves.

8. 8

   Testing

   Turn the key to prime the fuel system and check for leaks. Clear the F-174-01 fault code using your diagnostic tool and run the engine to verify the repair.