Case IH 19135 – Engine Control Unit (ECU): DEF/AdBlue quality sensor detects diesel fuel in DEF/AdBlue tank

The TULC sensor detects the acoustic signature of diesel fuel in the DEF tank, triggering a severe engine derate to protect the system from catastrophic fires or SCR destruction.

• Tier 4b
• Steiger
• Magnum
• Optum
• Puma
• Maxxum
• Axial-Flow 140 series
• Axial-Flow 240 series
• Patriot

1. 1

   Perform a visual and olfactory inspection of the DEF tank (look for an oily slick floating on top and smell for diesel).

2. 2

   Extract a fluid sample and test it using a DEF refractometer or contamination test kit (should read exactly 32.5% urea with a clear line).

3. 3

   If fluid is clean, inspect the wiring harness and connector at the DEF quality sensor for bent pins, corrosion, or rubbed wires that could cause a false reading.

1. 1

   Drain the System

   Completely drain the contaminated DEF tank.

2. 2

   Remove and Clean the Tank

   Remove the DEF tank from the machine. Thoroughly flush the inside of the tank with distilled water or a dedicated DEF system cleaner to remove all hydrocarbon residues.

3. 3

   Inspect/Replace the Sensor

   Remove the DEF tank header unit (which houses the quality sensor). If contamination was severe, the sensor unit must be replaced.

4. 4

   Flush the Lines

   Disconnect the DEF lines leading to the supply module (pump) and flush them with distilled water.

5. 5

   Replace Filters

   Remove and replace the main DEF supply module filter, as it will be contaminated with diesel.

6. 6

   Reassemble and Refill

   Reinstall the tank, sensor, and lines. Refill the tank with fresh, known-good DEF that meets the ISO 22241 standard.

7. 7

   Software Reset

   Connect the Case IH Electronic Service Tool (EST) to clear the fault code and perform an Inducement Unlock / Counter Reset.

8. 8

   Verification

   Run the machine under load to verify the code does not return and the derate is lifted.