Case IH 19168 – Engine Control Unit (ECU) or Dosing Control Unit (DCU): DEF/AdBlue quality sensor internal failure (Temperature sensor value is lower than expected)

The DEF quality sensor internal temperature sensor registers a value that is lower than the expected operating range, flagging an internal failure. If left unresolved, this emissions-related fault can lead to a severe engine derate, potentially entering an 'Emergency Re-start' mode which only allows 30 seconds of operation before forcing the engine back to low idle speed.

• Tier 4b
• 240 Series Axial-Flow Combines
• Magnum
• Steiger
• Puma
• 1021G
• 621G
• 821F
• 921F

1. 1

   Locate the Sensor: The DEF quality sensor is integrated into the machine's DEF delivery system and is positioned directly on or inside the DEF tank / injection header module.

2. 2

   Inspect Wiring and Connections: Check the wiring harness leading to the DEF tank header for chafing, corrosion, or disconnected pins. A short to a low source or an open circuit can cause the temperature reading to drop below normal parameters.

3. 3

   Check Fluid Condition: Ensure the DEF/AdBlue is not frozen, degraded, or contaminated, as extreme cold or poor fluid quality can trigger erratic sensor readings.

4. 4

   Compare Temperature Readings: Use the Case IH Electronic Service Tool (EST) to monitor the live DEF temperature value and compare it against the ambient temperature. If the sensor reads an impossibly low value (e.g., absolute zero) while ambient temps are normal, the internal thermistor has failed.

1. 1

   Prepare machine for repair

   Turn off the machine, disconnect the battery, and ensure the DEF system has completed its purge cycle.

2. 2

   Clean sensor area

   Locate the DEF tank and clean the area around the DEF quality sensor/header to prevent dirt from entering the tank.

3. 3

   Disconnect electrical connector

   Disconnect the electrical connector from the DEF quality sensor.

4. 4

   Disconnect fluid lines

   Disconnect the DEF supply and return lines from the header unit (be prepared to catch minor fluid spills).

5. 5

   Remove old sensor assembly

   Unscrew the mounting ring or retaining bolts securing the sensor to the DEF tank and carefully extract the old sensor assembly.

6. 6

   Install new sensor

   Install the new OEM DEF quality sensor, ensuring the rubber gasket/O-ring is properly seated to prevent leaks.

7. 7

   Reconnect lines and harness

   Reconnect the fluid lines and the electrical harness.

8. 8

   Reconnect battery and clear codes

   Reconnect the battery. Connect the Case IH EST diagnostic tool to clear fault code 19168 and reset the DEF system monitors.