John Deere 1761.04 – ECU: DEF Tank Fluid Level Sensor, Voltage Too Low

The voltage signal from the Diesel Exhaust Fluid (DEF) tank level sensor has dropped below the normal operating range, typically caused by a short to ground in the sensor circuit or an internal short circuit within the DEF tank sensor itself.

• 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
• 9470RT
• 9520RT
• 9570RT
• 6105M
• 6120E

1. 1

   Connect a diagnostic tool and check the DEF tank level reading. If it reads exactly 0% despite having fluid, a sensor connection failure, corrosion, or a dead short is highly likely.

2. 2

   Inspect the DEF tank sensor wiring harness (e.g., the Left Main Harness W3 on G-Series loaders) for chafing, pinched wires, or damage that could cause a short to the machine's chassis (ground).

3. 3

   Disconnect the DEF tank header/sensor plug. Check for water intrusion, bent pins, or corrosion inside the connector.

4. 4

   Use a multimeter to measure the voltage at the sensor connector (key ON, engine OFF). Verify if the voltage is being pulled to ground. If the harness tests fine and shows no shorts to ground when disconnected, the internal circuitry of the DEF sensor is shorted.

1. 1

   Drain the DEF Tank

   If the sensor requires replacement, drain the Diesel Exhaust Fluid from the tank to avoid spills.

2. 2

   Repair Wiring

   If the diagnostic tests revealed a short to ground in the harness, repair or replace the damaged section of the wiring harness.

3. 3

   Replace the DEF Tank Sensor/Header

   If the harness is intact, the sensor itself has an internal short. Disconnect the fluid lines and electrical connector, unbolt the header from the top of the tank, and install the new assembly.

4. 4

   Replace Filters

   It is highly recommended to replace the DEF header inlet filter (e.g., DZ111004 or AT502964) while the header is removed.

5. 5

   Refill and Prime

   Refill the tank with fresh, uncontaminated DEF.

6. 6

   Clear Codes and Calibrate

   Reconnect the diagnostic tool, clear the ECU 001761.04 code, and perform a DEF Level Calibration. Ensure the dashboard gauge now reads the correct fluid level.