Case IH F-1761-11 - ECU – Engine Control Unit (ECU): DEF/AdBlue level too low warning is active - Stage 2

This code indicates that the Diesel Exhaust Fluid (DEF) level has dropped below the critical minimum threshold (or the sensor is erroneously reporting it as empty). The "Stage 2" designation means the machine's emissions system has triggered a severe engine derate or torque limitation to comply with environmental regulations, which will restrict the machine's operational power until the issue is resolved.

• MAGNUM AFS Connect
• Magnum AFS Connect Series
• Magnum 400
• 240 Series Axial-Flow Combines
• 7240
• 8240
• 9240
• Steiger Series
• Steiger 500
• 555 Quadtrac
• Puma Series
• Farmall Series

1. 1

   Physical Fluid Level Check: Do not rely solely on the in-cab gauge. Visually and physically inspect the DEF/AdBlue tank to confirm if it is actually empty.

2. 2

   Wiring and Connector Inspection: Check the wiring harness and connectors going to the DEF tank level sensor (integrated into the DEF header unit) for damage, corrosion, or rodent damage. Look for related circuit codes that might indicate a wiring failure, such as SPN 1761 FMI 3 (voltage above normal/open circuit) or SPN 1761 FMI 4 (voltage below normal/short to ground).

3. 3

   Sensor Verification via Scan Tool: Use an OBD-II or Case IH diagnostic scan tool to monitor the DEF level sensor's live data output. If the tank is physically full but the sensor reads empty, the sensor/DEF header unit has failed internally.

4. 4

   Fluid Quality Check: Ensure the DEF fluid is not crystallized or contaminated. Crystallized DEF can cause the float or ultrasonic sensor in the DEF header to stick, falsely reporting an empty tank.

1. 1

   Refill the DEF Tank

   If the tank is genuinely empty, fill it with fresh, high-quality Diesel Exhaust Fluid. Turn the key to the ON position and wait to see if the level registers and the code clears.

2. 2

   Clear Codes

   If the tank was filled but the machine is still derated, use a diagnostic tool to clear the F-1761-11 code and reset the SCR system Stage 2 derate.

3. 3

   Replace the DEF Level Sensor / Header Unit

   If the sensor has failed: Turn off the machine and disconnect the negative battery cable.

4. 4

   Clean area

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

5. 5

   Drain tank

   Drain the DEF tank if necessary, or ensure the fluid level is below the sensor mounting flange.

6. 6

   Disconnect lines and connector

   Disconnect the electrical connector and the DEF supply/return lines from the top of the DEF header unit.

7. 7

   Remove mounting hardware

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

8. 8

   Extract header

   Carefully extract the DEF header assembly from the tank.

9. 9

   Install new header

   Install the new DEF level sensor/header unit using a new gasket/seal to prevent leaks and contamination.

10. 10

    Reinstall hardware

    Reinstall the retaining ring or bolts.

11. 11

    Reconnect lines and connector

    Reconnect the fluid lines and the electrical connector.

12. 12

    Finalize repair

    Refill the tank, reconnect the battery, and use a diagnostic tool to clear the fault codes and perform any required SCR system resets.