Case IH 19159 – Engine Control Module (ECM) or Dosing Control Unit (DCU): DEF/AdBlue quality sensor internal failure (Concentration value is higher than expected)

The DEF quality sensor is reading a urea concentration significantly higher than the acceptable 32.5% threshold. This can occasionally be caused by water evaporating from the DEF tank, but is most commonly caused by an internal failure of the sensor itself due to ammonia gas seeping into the housing and corroding the internal circuit board.

• Tier 4b
• 240 Series Axial-Flow Combines
• Steiger
• Quadtrac
• Magnum
• Optum
• Puma
• Maxxum

1. 1

   Test the DEF fluid currently in the tank using a DEF refractometer to verify if the urea concentration is higher than 32.5% due to evaporation.

2. 2

   Inspect the wiring harness and connector leading to the DEF header unit for chafing, broken wires, or heavy corrosion inside the connector pins.

3. 3

   Check with a Case IH dealer to see if an ECM software update is available for your specific model that bypasses the DEF quality sensor entirely.

1. 1

   Turn off machine and disconnect battery

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

2. 2

   Clean DEF tank area

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

3. 3

   Disconnect electrical connector

   Disconnect the electrical connector from the DEF header unit.

4. 4

   Disconnect DEF lines

   Disconnect the DEF supply and return lines from the header. (Be prepared with a rag, as a small amount of DEF may spill. Wash any spilled DEF off the machine immediately with warm water, as it is highly corrosive).

5. 5

   Remove mounting hardware

   Remove the mounting bolts or unscrew the retaining locking ring holding the DEF header assembly to the tank.

6. 6

   Remove old DEF header

   Carefully pull the old DEF header/quality sensor assembly straight up and out of the tank.

7. 7

   Install new DEF header

   Install the new DEF header assembly, ensuring the rubber O-ring/gasket is properly seated to prevent leaks and ammonia gas escape.

8. 8

   Secure mounting hardware

   Secure the mounting bolts or locking ring.

9. 9

   Reconnect lines and connector

   Reconnect the DEF fluid lines and the electrical connector.

10. 10

    Clear fault code

    Reconnect the battery, turn the key on, and use a diagnostic scan tool to clear the 19159 fault code.