Case IH F-3031-01 - ECU – Engine Control Unit (ECU): DEF/AdBlue temperature sensor voltage is lower than expected

The control module is receiving a voltage signal from the Diesel Exhaust Fluid (DEF) temperature sensor that falls below the minimum calibrated threshold. This condition is almost always electrical and typically points to a short circuit to ground, a broken wire, severe corrosion at a connector, or an internal failure of the sensor itself.

• MAGNUM AFS Connect
• Axial-Flow Combines 140 Series
• Axial-Flow Combines 240 Series
• 7140
• 7240
• 8240
• 9240
• Magnum Series (235-340)
• Farmall Series
• 115U
• 40-50 CVT
• Austoft 9900 Sugarcane Harvesters

1. 1

   Inspect the wiring harness leading from the ECU to the DEF tank header unit for chafed wires, melted insulation, or pinch points along the chassis

2. 2

   Disconnect the DEF temperature sensor connector and check for water ingress, DEF fluid crystallization (corrosion), or pushed-back pins

3. 3

   Using a multimeter, check the sensor's signal wire for a short to ground

4. 4

   Verify that the sensor is receiving the correct 5V reference voltage from the ECU (if missing, the fault is in the wiring or ECU)

5. 5

   Check the resistance of the temperature sensor itself; if it reads out of specification or shows a dead short, the sensor has failed

1. 1

   Power Down

   Turn off the machine and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Access the Sensor

   Locate the DEF tank. The temperature sensor is typically integrated into the DEF tank sending unit (header assembly), which drops into the top of the tank.

3. 3

   Clean the Area

   Thoroughly clean the top of the DEF tank around the sensor assembly to prevent dirt from falling into the DEF fluid.

4. 4

   Remove the Assembly

   Disconnect the electrical harness and the DEF fluid lines. Unscrew the locking ring or mounting bolts holding the DEF header assembly in place and carefully pull it out of the tank.

5. 5

   Install the New Part

   Insert the new DEF temperature/quality sensor assembly into the tank. Secure the locking ring/bolts.

6. 6

   Reconnect

   Reattach the DEF fluid lines and plug in the electrical connector. Reconnect the battery.

7. 7

   Clear Codes and Test

   Use the Case IH Electronic Service Tool (EST) to clear the F-3031-01 fault code.

8. 8

   Verification

   Run the engine and perform an SCR system verification test (forced dosing test) to ensure the ECU is reading the correct DEF temperature and that no induction/derate states remain active.