Case IH F-1761-18 - ECU – Engine Control Unit (ECU): DEF tank LEVEL LOW

Indicates a physically low fluid level reading (moderately severe). If the DEF tank is physically full and F-1761-18 is active, it indicates that the DEF tank level sensor (or its circuit) has failed and is erroneously reporting an empty tank to the system.

• MAGNUM AFS Connect
• Farmall 90C
• Farmall 100C
• Farmall 130A
• Farmall 35C
• Maxxum 150 Multicontroller
• Steiger 550
• Steiger 555 Quadtrac
• Axial-Flow Combine 9230
• Puma
• Magnum

1. 1

   Physically check the DEF tank fluid level. If it is empty or very low, refill the tank with high-quality DEF and see if the code clears.

2. 2

   Inspect the wiring harness leading to the DEF header/sensor for pinches, fraying, or areas where it may be rubbing against metal components. Examine the connector for corrosion or bent pins.

3. 3

   Use a multimeter to verify that the 5V reference voltage and ground are present at the sensor connector.

4. 4

   Inspect the DEF tank for crystallized DEF deposits that could be binding the level sensor float or fouling the ultrasonic sensor.

5. 5

   Use a diagnostic tool to check for related circuit codes, such as SPN 1761 FMI 3 (voltage high/open circuit) or SPN 1761 FMI 4 (voltage low), which definitively point to an electrical failure.

1. 1

   Turn off the machine, remove the key, and disconnect the battery

   Prevents electrical shorts.

2. 2

   Locate the DEF tank and the DEF header unit

   Typically mounted to the top of the tank via a flange.

3. 3

   Thoroughly clean the area around the DEF header

   Prevents dirt or debris from falling into the tank during removal.

4. 4

   Disconnect the electrical harness connector from the DEF header.

5. 5

   Disconnect the DEF supply, return, and vent lines.

   Caution: DEF is corrosive to certain metals and plastics; clean up any spills immediately with warm water.

6. 6

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

7. 7

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

   Includes the pickup tubes and sensors.

8. 8

   Inspect the inside of the DEF tank.

   If contaminated or heavily crystallized, drain and flush the tank with deionized water before proceeding.

9. 9

   Insert the new DEF header assembly into the tank

   Ensure the new gasket is properly seated to prevent leaks.

10. 10

    Reinstall and tighten the mounting bolts or retaining ring.

11. 11

    Reconnect the DEF fluid lines and the electrical connector.

12. 12

    Reconnect the battery, turn the ignition on, and use an OBD-II/J1939 diagnostic scan tool to clear the fault codes.

13. 13

    Start the engine and verify that the DEF gauge reads the correct level

    Verify the machine is no longer in a derated power state.