John Deere 1761.03 – ECU: DEF Tank Fluid Level Sensor, Voltage Too High

This code is triggered when the controller detects that the voltage at the Diesel Exhaust Fluid (DEF) tank fluid level sensor is abnormally high. This typically indicates a short circuit to a 12V power source or an open circuit within the DEF level sensor wiring or the sensor itself. Because the sensor cannot accurately read the DEF level, the machine may derate engine power to comply with emissions regulations.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5090M
• 5100M
• 5100MH
• 5100ML
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 330G
• 331G
• 332G
• 333G
• 8R/8RT Series
• 8245R
• 8400R
• 9R/9RT/9RX Series
• 9470RT
• 9520RT
• 9570RT
• 6M Series
• 6R Series
• S-Series Combines
• R-Series Sprayers

1. 1

   Visually inspect the wiring harness leading to the DEF tank fluid level sensor for signs of chafing, damage, or wear that could cause a short to a power source or an open circuit.

2. 2

   Disconnect the sensor and use a multimeter to verify the voltage at the sensor connector. High voltage readings on the signal wire confirm a short to 12V.

3. 3

   Pin out the entire DEF level sensor circuit back to the ECU to check for shorts to the vehicle's power system or broken wires.

4. 4

   Verify if the DEF tank fluid level sensor float is physically stuck inside the tank.

1. 1

   Repair Wiring

   If the diagnostic tests reveal a short or open circuit in the machine's harness, repair or replace the damaged wiring.

2. 2

   Replace the Sensor/Header

   If the wiring harness tests good, the internal circuitry of the DEF level sensor has failed. The DEF level sensor is integrated into the DEF Tank Header Assembly. You must replace the entire DEF Tank Header.

3. 3

   Reassemble and Reconnect

   Install the new DEF Tank Header into the DEF tank, ensuring the O-ring/seal is properly seated, and reconnect the electrical connector and DEF lines.

4. 4

   Reset ECU

   After repairs are complete, use a diagnostic tool to reset the ECU and clear the error code.

5. 5

   Perform Diagnostic Tests

   Turn the key on and monitor the DEF level readings via the cab display or diagnostic tool to ensure the new sensor is functioning correctly and providing accurate fluid levels.