Case IH F-174-20 - ECU – Engine Control Unit (ECU): Fuel Temperature is too high

The system has detected that the diesel fuel temperature has exceeded the safe operating threshold (typically greater than 75°C / 167°F). The engine will typically derate its power output to protect the high-pressure fuel injector pump from severe damage caused by hot fuel losing its lubricating properties.

• MAGNUM AFS Connect
• Farmall series (105C, 110U, 115C, 120U)
• Maxxum MX series
• CX series
• CS and CS Pro series
• C series
• AFX series (AFX8010)

1. 1

   Check fuel level: Verify the fuel level in the tank. If the tank is nearly empty and the ambient temperature is high, the hot return flow from the engine can rapidly heat up the small amount of remaining fuel.

2. 2

   Visual wiring inspection: Inspect the fuel temperature sensor wiring harness for chafing, breaks, or short circuits to the ground.

3. 3

   Connector check: Disconnect the sensor and check for corrosion, moisture, or loose pins inside the connector.

4. 4

   Voltage test: Turn the key ON (engine off) and verify that the ECU is supplying the correct reference voltage (typically 5V) to the sensor connector.

5. 5

   Resistance test: Test the sensor's resistance with a multimeter. A properly functioning sensor should read approximately 1.9 kΩ at 20°C (68°F) and drop in resistance as it heats up. An open circuit or dead short indicates internal failure.

1. 1

   Prepare machine

   Turn off the machine, relieve any residual fuel system pressure if required by the specific engine manual, and allow the engine to cool completely.

2. 2

   Locate sensor

   Locate the fuel temperature sensor. Depending on the engine model, it is typically mounted on the fuel rail, the fuel filter housing, or directly on the high-pressure injection pump housing.

3. 3

   Disconnect harness

   Depress the locking tab and disconnect the electrical wiring harness from the sensor.

4. 4

   Remove sensor

   Carefully unscrew the sensor using a wrench. Have a shop rag ready to catch any minor diesel fuel spillage.

5. 5

   Clean port

   Clean the mounting port threads to ensure a good seal and prevent contamination from entering the fuel system.

6. 6

   Install new sensor

   Thread in the new fuel temperature sensor by hand to prevent cross-threading, then tighten it to the manufacturer's specified torque.

7. 7

   Reconnect harness

   Reconnect the electrical harness, ensuring the locking tab clicks securely into place.

8. 8

   Verify repair

   Turn the ignition key on, clear the F-174-20 fault code using a diagnostic scan tool, and run the engine to verify the repair. Inspect the sensor area for any fuel leaks.