Case IH 19167 (DTC 1A4E) - ECU – Engine Control Unit (ECU): DEF/AdBlue quality sensor internal failure (Temperature sensor value is higher than expected)

The DEF/AdBlue quality sensor is a multi-function unit that measures fluid level, fluid quality/concentration, and fluid temperature. This specific code triggers when the internal temperature thermistor reports a value that exceeds the maximum expected physical range, usually pointing to an internal hardware failure of the sensor itself rather than an actual overheating fluid condition.

• MAXXUM T4E
• 240 Series Axial-Flow Combines (5140, 7240, 8240)
• Magnum series tractors (Magnum 340)
• Steiger series tractors

1. 1

   Inspect the Wiring and Connector: Check the wiring harness leading to the DEF head unit for chafing, shorts to voltage, or moisture intrusion.

2. 2

   Check for Related Codes: Look for accompanying codes such as 1B4E (minimum signal range) or 4C4E (general temperature sensor failure).

3. 3

   Evaluate DEF Quality: Check the tank for debris, crystallization, or contamination, as inadequate quality fuel or contaminated DEF can cause chemical reactions that damage internal sensors.

4. 4

   Live Data Monitoring: Use a diagnostic scan tool to read the live DEF temperature data to see if the reading is erratic or locked at an impossibly high temperature while the tank is cool.

1. 1

   Preparation

   Turn off the machine, disconnect the battery, and allow the SCR/DEF system to depressurize and cool down.

2. 2

   Locate the Sensor

   Locate the DEF Head Unit, which is mounted directly to the top of the DEF/AdBlue tank.

3. 3

   Clean the Area

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

4. 4

   Disconnect Lines

   Carefully disconnect the electrical harness connector. Then, disconnect the DEF suction/return lines and the engine coolant lines (which run through the head unit to thaw frozen DEF).

5. 5

   Remove the Sensor

   Remove the mounting hardware (typically M6 hex socket screws) securing the sensor to the tank. Carefully pull the old DEF quality sensor assembly straight up and out of the tank.

6. 6

   Install the New Sensor

   Insert the replacement DEF quality sensor, ensuring the rubber gasket/seal is properly seated to prevent leaks.

7. 7

   Reassembly

   Fasten the mounting screws. Reconnect the coolant lines, DEF fluid lines, and the electrical connector.

8. 8

   Refill and Clear Codes

   If the DEF was contaminated, drain the tank and refill it with fresh, high-quality DEF. Reconnect the battery, turn the key on, and use a diagnostic tool to clear fault code 19167 (1A4E).