Case IH 19169 (DTC 4C4E) - ECU – Engine Control Unit (ECU) / SCR Control Module: DEF/AdBlue quality sensor internal failure (Temperature sensor failure)

The DEF/AdBlue quality sensor (often integrated into the DEF tank header unit) contains an internal temperature sensor. This code triggers when the sensor's temperature signal fails or goes out of range (reported via the CAN structure ComRx_CRI1). Because the Selective Catalytic Reduction (SCR) system relies on accurate temperature readings to determine the state and quality of the Diesel Exhaust Fluid (DEF), this internal failure prevents the system from functioning correctly and will typically lead to an engine power derate.

• MAXXUM T4E
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Farmall C
• Maxxum
• Puma
• Magnum
• Optum

1. 1

   Visually inspect the wiring harness and electrical connector at the DEF/AdBlue quality sensor (located on top of the DEF tank) for physical damage, corrosion, or loose pins

2. 2

   Verify power, ground, and CAN bus communication to the sensor

3. 3

   Check for related fault codes, such as DTC 4DCA (which indicates the temperature of the DEF quality sensor is different from the DEF level temperature)

4. 4

   If the wiring harness and CAN communication are intact, verify that the sensor unit itself has failed internally (cannot be serviced independently of the header assembly)

1. 1

   Preparation

   Turn off the machine, remove the key, and disconnect the battery to ensure safety.

2. 2

   Clean the Area

   Locate the DEF/AdBlue tank. Thoroughly clean the area around the DEF header/quality sensor to prevent dirt or debris from contaminating the DEF tank during removal.

3. 3

   Drain Fluid (if necessary)

   If the DEF fluid level is above the sensor mounting point, drain the tank until the level is below the opening.

4. 4

   Disconnect Lines

   Carefully disconnect the electrical connector from the DEF quality sensor. Then, disconnect the DEF supply and return lines from the sensor header.

5. 5

   Remove the Sensor

   Remove the mounting bolts or the retaining ring securing the DEF quality sensor to the tank. Carefully extract the old sensor assembly by pulling it straight up.

6. 6

   Install the New Sensor

   Insert the new DEF quality sensor (header unit) into the tank, ensuring the gasket/O-ring is properly seated to prevent leaks.

7. 7

   Secure and Reconnect

   Tighten the mounting bolts or retaining ring to OEM torque specs. Reconnect the DEF fluid lines and the electrical connector.

8. 8

   Refill

   Refill the DEF tank with fresh, high-quality Diesel Exhaust Fluid.

9. 9

   Clear Codes and Test

   Reconnect the battery and turn on the ignition. Use a diagnostic tool (such as the CNH Electronic Service Tool) to clear the fault codes. Run the engine and perform an SCR system test to verify the repair and ensure there are no leaks.