Massey Ferguson 003031.10 – EEM4: DEF Tank Temperature Sensor Abnormal Change Rate

The engine control system has detected that the temperature value from the DEF tank temperature sensor is changing at an illogical or unbelievable rate, particularly during the heating process. The system expects a gradual temperature increase as the heater works; a sudden spike or drop indicates a fault with the sensor or its circuitry. This is an emission-related fault that will illuminate a warning lamp and can lead to a reduction in engine power.

• MF 5700 S Series
• MF 6700 S Series
• MF 7700 S Series
• MF IDEAL Combines
• MF 4710

1. 1

   Inspect the wiring harness and connectors between the DEF tank sensor and the engine ECU for loose connections, corrosion in the pins, chafing, or breaks

2. 2

   Check for other active fault codes related to the DEF level sensor, DEF quality sensor, or open/short circuits in the aftertreatment system, which can indicate a shared wiring or power supply issue

3. 3

   Verify the DEF in the tank is not frozen, as this can affect heating and sensor readings

4. 4

   Check that the DEF concentration is correct (32.5%) using a refractometer

5. 5

   Disconnect the sensor and measure the resistance across its terminals using a multimeter (a reading of zero ohms suggests a short circuit, while infinite resistance indicates an open circuit)

6. 6

   Clear the fault codes, turn the ignition off for at least 60 seconds, and operate the machine through several drive cycles to see if the fault returns

1. 1

   Prepare machine

   Ensure the engine is off and the battery is disconnected.

2. 2

   Access and clean sensor area

   Remove access panels or other components to reach the top of the DEF tank. Thoroughly clean the area around the sensor head to prevent contamination of the DEF tank upon removal.

3. 3

   Disconnect lines and harness

   Carefully disconnect the electrical harness, as well as any DEF and engine coolant lines connected to the sensor head assembly. Cap the lines to prevent spills and contamination.

4. 4

   Remove the sensor unit

   Remove the locking ring or bolts securing the sensor unit and carefully lift the sensor assembly out of the tank.

5. 5

   Install the new sensor

   Install the new sensor with a new gasket or sealing ring. Tighten the retaining ring or bolts to the manufacturer's specified torque.

6. 6

   Reconnect and finalize

   Reconnect the electrical harness and all fluid lines. Refill the DEF tank if necessary. Reinstall any access panels, reconnect the battery, and perform a system reset to clear the fault code. Run the engine and monitor for leaks or recurring faults.