John Deere 3031.3 – Engine Control Unit (ECU): DEF Tank Fluid Temperature Signal Out of Range High

The controller is receiving a voltage signal from the Diesel Exhaust Fluid (DEF) tank temperature sensor that exceeds the maximum expected threshold. This condition typically indicates an open circuit, a disconnected sensor, or a short to a 12V power source in the sensor's wiring circuit.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5090M
• 5100M
• 5100MH
• 5100ML
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6R
• 6M
• 7R
• 8R
• 9R
• 9RT
• 9RX
• 7230R
• 9470RT
• T-Series
• W-Series
• T550
• W235
• R4023
• R4030
• R4038
• R4045
• K-Series Dozers
• L-Series Dozers
• 450K
• 550K
• 710L
• Graders
• Excavators

1. 1

   Inspect the wiring harness running from the ECU to the DEF tank header assembly for chafed wires, melted insulation, or pinch points that could cause a short to power.

2. 2

   Disconnect the DEF tank header connector and check for water intrusion, corrosive DEF crystal buildup, or bent/pushed-back pins.

3. 3

   Use a multimeter to check the temperature sensor signal wire for continuity to the ECU and ensure it is not shorted to a 12V power wire.

4. 4

   Test the resistance of the temperature sensor pins on the DEF header itself. An open reading (infinite resistance) confirms the sensor has failed internally.

1. 1

   Preparation

   Turn off the machine, remove the key, and disconnect the negative battery cable.

2. 2

   Access the Tank

   Locate the DEF tank and clean the area around the top of the DEF header assembly thoroughly to prevent dirt or debris from falling into the tank.

3. 3

   Drain Fluid

   If the DEF tank is completely full, drain enough fluid so the level is below the header mounting hole.

4. 4

   Disconnect Lines

   Carefully disconnect the electrical connector and the DEF suction and return lines from the top of the header. Cap the lines immediately to prevent contamination.

5. 5

   Remove the Header

   Remove the retaining ring, locking collar, or mounting bolts holding the header to the tank. Carefully pull the old header assembly straight up and out of the tank.

6. 6

   Install the New Header

   Lubricate the new O-ring/seal with a small amount of clean DEF (do not use grease or oil). Carefully lower the new DEF Tank Header Assembly into the tank.

7. 7

   Secure and Reconnect

   Secure the retaining ring/bolts. Reconnect the DEF lines (ensuring they click into place) and the electrical connector.

8. 8

   Finalize

   Reconnect the battery, turn the key on, and use John Deere Service ADVISOR (or a compatible heavy-duty scan tool) to clear the 003031.3 fault code. Run the engine to verify the code does not return and that the DEF temperature reads accurately.