Case IH F-1761-31 - ECU – Engine Control Unit (ECU): Remaining DEF/AdBlue is below the empty threshold.

This code indicates that the Diesel Exhaust Fluid (DEF) level in the tank has dropped below the critical Level 3 (Zone 3) empty threshold. When this code is triggered, the machine's control system will initiate a severe engine derate (often limiting the engine to low idle or 1000 RPM and causing a 100% power loss) to prevent the Selective Catalytic Reduction (SCR) system from operating without fluid.

• MAGNUM AFS Connect
• Magnum
• Steiger
• Optum
• Puma
• Maxxum
• Farmall
• Axial-Flow 140 Series
• Axial-Flow 150 Series
• Axial-Flow 240 Series
• Axial-Flow 250 Series
• Axial-Flow 7240
• Axial-Flow 8240
• Axial-Flow 9240
• Patriot
• Trident

1. 1

   Physically inspect the DEF tank to verify if it is genuinely empty, rather than relying solely on the cab gauge.

2. 2

   Check the DEF tank, lines, and the DEF supply module (pump) for physical leaks or white crystalline buildup.

3. 3

   If the tank is full but the gauge reads empty, suspect a failed DEF level sensor or stuck float.

4. 4

   Inspect the wiring harness and electrical connector at the top of the DEF tank (DEF header) for corrosion, chafing, or loose pins.

5. 5

   Use a diagnostic tool (like Case IH AFS Service Tool or Jaltest) to read live data from the DEF level sensor to see if the voltage/percentage is stuck at 0%.

1. 1

   Refill DEF tank

   Refill the DEF tank with high-quality, uncontaminated Diesel Exhaust Fluid (AdBlue).

2. 2

   Turn ignition ON

   Turn the ignition key to the ON position and wait. In many cases, the system will recognize the new fluid level and clear the active derate automatically.

3. 3

   Clear fault codes

   If the code remains latched, connect a diagnostic scan tool to clear the fault codes and reset the SCR system.

4. 4

   Disconnect battery

   If the tank is full but the sensor has failed (DEF Header Replacement), turn off the machine and disconnect the negative battery cable.

5. 5

   Clean tank area

   Clean the area around the top of the DEF tank thoroughly to prevent dirt from falling into the tank.

6. 6

   Disconnect electrical connector

   Disconnect the electrical connector from the DEF header unit.

7. 7

   Disconnect lines

   Disconnect the DEF suction/return lines and the engine coolant lines (which heat the DEF) from the header. Note: Cap the coolant lines to prevent fluid loss, and wash away any spilled DEF immediately with warm water.

8. 8

   Remove mounting hardware

   Remove the mounting bolts or the retaining lock ring securing the DEF header to the tank.

9. 9

   Remove old DEF header

   Carefully pull the old DEF header assembly vertically out of the tank.

10. 10

    Insert new DEF header

    Insert the new DEF header assembly, ensuring the rubber O-ring/gasket is properly seated to prevent leaks.

11. 11

    Reinstall mounting hardware

    Reinstall the retaining ring or bolts.

12. 12

    Reconnect lines and connector

    Reconnect the DEF lines, coolant lines, and electrical connector.

13. 13

    Verify and clear codes

    Reconnect the battery, turn the key on, and verify the DEF gauge now reads correctly. Clear the fault codes using a diagnostic tool.