Case IH 19159 (DTC 144E) - ECU – Engine ECU (Electronic Control Unit): DEF/AdBlue quality sensor internal failure (concentration value is higher than expected)

The DEF (Diesel Exhaust Fluid) quality sensor is reading a urea concentration level that exceeds the maximum expected threshold. This is typically caused by an internal failure of the sensor itself (often due to ammonia gas corroding the internal circuit board) or, less commonly, severely degraded/evaporated DEF fluid that has left a disproportionately high urea concentration.

• MAXXUM T4E
• Case IH 240 Series Axial-Flow Combines
• Case IH Quadtrac (500, 620)
• Steiger
• Magnum
• Optum
• Puma (130-240)
• Maxxum (110-150)
• Farmall C series (90C-120C)

1. 1

   Test the DEF fluid in the tank using a refractometer to ensure the urea concentration is at the standard 32.5 percent. If contaminated or evaporated, drain, flush, and refill.

2. 2

   Inspect the wiring harness and female electrical connector at the DEF header for signs of corrosion, moisture, or damage caused by ammonia gas.

3. 3

   Check with a dealer for available software updates. CNH has released updates for certain models that bypass the DEF quality sensor entirely, relying on NOx sensors instead.

1. 1

   Turn off the machine and disconnect the battery to prevent electrical shorts.

   Ensure the machine is completely powered down before beginning work.

2. 2

   Locate the DEF quality sensor/header unit, which is mounted on the DEF tank.

   Identify the sensor assembly on the tank.

3. 3

   Disconnect the electrical connector (female plug) from the sensor.

   Carefully unplug the harness from the sensor unit.

4. 4

   Disconnect the DEF suction and return hoses from the header unit.

   Remove the fluid lines attached to the header.

5. 5

   Unscrew or unbolt the DEF header assembly from the top/bottom of the DEF tank.

   The orientation depends on the specific model's tank design.

6. 6

   Carefully extract the old sensor/header unit from the tank.

   Pull the unit out without damaging the surrounding components.

7. 7

   Insert the new DEF quality sensor/header unit into the tank.

   Ensure the gasket/O-ring is properly seated to prevent ammonia gas leaks.

8. 8

   Secure the unit and reconnect the DEF lines and the electrical harness.

   Fasten the assembly and reattach all hoses and connectors.

9. 9

   Reconnect the battery, turn on the ignition, and clear the stored 19159 / 144E fault codes.

   Use an AFS Pro display or electronic service tool (EST) to clear the codes.