Case IH 19524 – Engine Control Unit (ECU) / Engine Control Module (ECM): DEF/AdBlue temperature sensor voltage is higher than expected.

The control module is receiving a voltage signal from the Diesel Exhaust Fluid (DEF) temperature sensor that exceeds the normal calibrated operating range. This usually points to an open circuit, a short circuit to a high-voltage source, or an internal failure of the DEF temperature sensor itself.

• Tier 4b
• 240 Series Axial-Flow Combines
• Farmall Tractors (40-45-50, 115U)
• Maxxum Tractors
• Puma Tractors
• Steiger Tractors
• N-Series TLBs

1. 1

   Inspect the DEF tank header/sensor connector and the wiring harness leading back to the ECU for physical damage, corrosion, or loose pins.

2. 2

   Check for an open circuit or a short to battery voltage on the sensor signal wire (Pin 1 routing to Pin 31 on ECU Connector-1, and verify reference ground on Pin 39).

3. 3

   Measure the resistance of the DEF temperature sensor (should be approximately 1.3 K Ω at 65°F/18°C). An open reading indicates sensor failure.

4. 4

   Connect the CNH EST diagnostic tool to monitor live DEF temperature sensor voltage and temperature readings to confirm the erratic or pegged high-voltage signal.

1. 1

   Preparation

   Park the machine on level ground, turn off the engine, and disconnect the battery.

2. 2

   Clean the Area

   Thoroughly clean the area around the top of the DEF tank to prevent dirt or debris from contaminating the DEF fluid, which can cause costly damage to the SCR system.

3. 3

   Disconnect Lines

   Carefully disconnect the DEF suction, return, and coolant heating lines from the DEF header.

4. 4

   Remove the Sensor

   Unplug the electrical connector and unbolt/unscrew the DEF header assembly from the tank.

5. 5

   Install New Part

   Insert the new DEF header/sensor assembly into the tank and secure it. Reconnect all fluid lines and the electrical connector.

6. 6

   System Reset

   Reconnect the battery. Because fault code 19524 triggers an SCR inducement (engine derate/power loss), you must use the CNH EST diagnostic tool to perform an 'Inducement Unlock / Counter Reset' once the physical repair is complete.