Case IH 19170 – Engine Control Module (ECM) or SCR/DEF Dosing Control Unit (DCU): DEF/AdBlue Quality Sensor - Physical Range Check error for Conductivity

The DEF (Diesel Exhaust Fluid) quality sensor is reading a conductivity value that falls outside the physically possible or expected range. This typically means either the DEF fluid is severely degraded/contaminated or the internal electronics of the DEF quality sensor have failed.

• Tier 4b
• Case IH Combines (e.g., 240 series)
• Case IH Steiger and Magnum tractors
• Case IH Farmall models with CVT transmissions
• Other equipment utilizing FPT Tier 4 engines

1. 1

   Test the DEF fluid using a DEF refractometer to ensure the urea concentration is exactly 32.5%.

2. 2

   Inspect the DEF fluid for contamination, such as cloudiness, dirt, or a diesel fuel odor (diesel fuel contamination will permanently damage the sensor).

3. 3

   Inspect the electrical harness and connector at the DEF header unit for corrosion, moisture intrusion, or chafed wires that could cause a false out-of-range signal.

4. 4

   Scan for related codes (such as 19142 or 19144) which indicate the sensor unit itself is internally shorted or dead.

1. 1

   Clean the Area

   Thoroughly clean the top of the DEF tank around the header unit to prevent dirt or debris from falling into the tank during removal.

2. 2

   Drain the Tank (If Contaminated)

   If the DEF was found to be contaminated or degraded, completely drain the tank and flush it with distilled water.

3. 3

   Disconnect Lines

   Carefully disconnect the DEF supply and return lines from the top of the header unit.

4. 4

   Disconnect Electrical

   Unplug the main electrical connector from the DEF quality sensor.

5. 5

   Remove the Sensor Assembly

   Unscrew the retaining ring or unbolt the flange holding the DEF header assembly to the tank. Carefully pull the entire sending unit straight up and out of the tank.

6. 6

   Install the New Part

   Insert the replacement DEF quality sensor/header unit into the tank. Ensure the rubber O-ring or gasket is properly seated to prevent leaks, and tighten the retaining ring.

7. 7

   Reconnect

   Reattach the DEF fluid lines and plug in the electrical connector.

8. 8

   Refill and Clear Codes

   Refill the tank with fresh, high-quality DEF. Use a diagnostic scan tool to clear the 19170 fault code. Cycle the key and run an SCR system test to verify the new sensor is communicating properly and the code does not return.