Case IH 19095 – Engine Control Unit (ECU): DEF/AdBlue tank temperature sensor plausibility failure

The control module is receiving a temperature reading from the Diesel Exhaust Fluid (DEF) tank that does not make logical sense (e.g., the reading is physically impossible, contradicts other ambient temperature sensors, or is changing at an erratic rate).

• Tier 4b
• Case IH 240 Series Axial-Flow Combines
• Case IH / CNH N Series Loaders
• Equipment utilizing FPT NEF T4F (Tier 4 Final) engines

1. 1

   Inspect the DEF level/temperature sensor connector and the Dosing Module connector for moisture, corrosion, or loose pins.

2. 2

   Check for contamination in the DEF tank, such as inadequate quality DEF or diesel fuel, which can cause chemical reactions that damage the sensor.

3. 3

   Verify environmental conditions to ensure the DEF is not frozen solid and the machine is not operating in extreme conditions causing temporary erratic readings.

4. 4

   Pin out the wiring harness between the DEF tank sensor and the ECU to ensure there is no intermittent short to ground or short to battery.

1. 1

   Power down the machine and disconnect the battery.

2. 2

   Locate the DEF Head Unit on the top of the DEF/AdBlue tank.

3. 3

   Disconnect the electrical connector and the DEF fluid lines from the head unit.

4. 4

   Remove the mounting hardware securing the unit to the tank and carefully extract the old assembly.

5. 5

   Install the new DEF Head Unit assembly, ensuring the gasket/seal is properly seated to prevent contamination.

6. 6

   Reconnect the fluid lines and the electrical connector.

7. 7

   Use a diagnostic service tool (such as the CNH Electronic Service Tool) to perform an 'Inducement Unlock / Counter Reset'.

   Because this fault causes an emissions inducement (engine derate), the engine will remain derated until this reset is performed.