John Deere 1761.18 – ECU: DEF Tank Fluid Level Moderately Low / Diesel Exhaust Fluid is Very Low

The system has detected that the Diesel Exhaust Fluid (DEF / AdBlue) tank fluid level has dropped below a critical threshold (typically below 10% or 0%, depending on the specific machine's programming). When this code is active, the machine will typically enter a derate mode, reducing engine performance and speed 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
• 260E
• 310E
• 9470RT
• 9520RT
• 9570RT
• STS10
• STS12
• STS14
• STS16
• 130G
• 160GLC
• 210GLC
• 250GLC
• 300GLC
• 350GLC
• 380GLC

1. 1

   Visually and physically verify the actual fluid level in the DEF tank. Do not rely solely on the electronic gauge.

2. 2

   Examine the DEF tank, filler neck, dosing unit, and associated lines for any signs of leaks, crystallization (white crust), or physical damage that could cause rapid fluid loss.

3. 3

   Ensure the DEF level sensor is accurately reading the fluid level. Check the ECU for related sensor circuit fault codes, such as SPN 1761 FMI 3 (Voltage Too High / Open Circuit) or SPN 1761 FMI 4 (Voltage Too Low / Short to Ground).

4. 4

   Inspect the wiring harness and connector at the DEF tank header assembly for corrosion, damage, or loose pins.

1. 1

   Refill the Tank

   Fill the DEF tank with high-quality Diesel Exhaust Fluid to well above the 10% threshold (preferably full).

2. 2

   Cycle the Ignition

   Turn the ignition key to the ON position (engine off) and wait a few moments to allow the ECU to poll the sensor and read the new fluid level.

3. 3

   Start the Engine

   Start the machine and monitor the system. The ECU should recognize the refilled tank, clear the active warning, and restore normal engine power.

4. 4

   Reset the ECU (If Necessary)

   If the code remains active after refilling, use a John Deere Service ADVISOR diagnostic scan tool to clear the error log and reset the ECU.

5. 5

   Replace the Sensor (If Faulty)

   If the tank is full but the ECU still reads empty (and wiring has been verified as good), the DEF tank level sensor has failed. On most John Deere equipment, the sensor is integrated into the DEF Tank Header Assembly, which must be replaced as a single unit.