John Deere 1761.17 – Engine Control Unit (ECU): DEF Tank Fluid Level Moderately Low

The Engine Control Unit (ECU) has detected a low level of Diesel Exhaust Fluid (DEF) in the tank. This is the least severe warning level for this issue. Initially, an amber warning light will illuminate and a diagnostic trouble code will be displayed. If the DEF level continues to decrease and approaches empty, the warning will become more severe, the light may flash, and the engine will derate, limiting its power and speed. To restore normal operation, the DEF tank must be refilled.

• 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 series
• 7R series
• 8R series
• 9R series
• 8R 410
• 6105M
• 6230R
• 6250R
• 9470RT
• 9520RT
• 9570RT
• S680
• S780
• T550
• T560
• T660
• T670
• W540
• W550
• 8400
• 8600
• 9800
• STS series
• R4030
• R4038
• R4044
• R4045
• R4060
• 130G
• 160GLC
• 180GLC
• 210GLC
• 250GLC
• 300GLC
• 350GLC
• 380GLC

1. 1

   Verify Physical Fluid Level: Check the actual fluid level in the DEF tank to confirm if it is genuinely low.

2. 2

   Verify DEF Quality: Ensure the tank is filled with ISO 22241-certified DEF. Use a refractometer to test the concentration (it should be approximately 32.5%).

3. 3

   Inspect for Leaks: Check the DEF tank, lines, and dosing unit for physical leaks or white crystallized deposits that indicate a leak.

4. 4

   Check the Sensor Reading: Use a diagnostic tool (like John Deere Service Advisor) to monitor the DEF level sensor. If the tank is full but the sensor reading is erratic (e.g., jumping from 0% to 80%) or stuck below 10%, the float/sensor inside the DEF tank header is faulty.

5. 5

   Inspect Wiring: Check the electrical wiring harness and connectors going to the DEF tank header for damage, corrosion, or poor grounding.

1. 1

   Refill the Tank

   Fill the DEF tank with high-quality, uncontaminated DEF.

2. 2

   Cycle the Ignition

   Turn the ignition key off and back on to see if the system resets and clears the code.

3. 3

   Replace the DEF Tank Header

   If the tank is full but the code remains active (indicating a failed level sensor), the DEF tank header assembly must be replaced.

4. 4

   Drain the Tank

   Drain the DEF fluid from the tank to prevent spills during removal.

5. 5

   Disconnect Header

   Disconnect the electrical harness and the fluid lines from the top of the DEF tank header.

6. 6

   Remove and Install

   Unbolt/unscrew the old DEF tank header assembly and carefully extract it from the tank. Insert the new header assembly, ensuring the gasket/seal is properly seated, and secure it.

7. 7

   Reconnect and Refill

   Reconnect the fluid lines and electrical harness. Refill the DEF tank.

8. 8

   Clear Codes

   Use John Deere Service Advisor (or a compatible J1939 diagnostic tool) to clear the active DTCs and verify the fault does not return.