Case IH 19153 (DTC 624E) - ECU – Engine Control Module (ECM) or Dosing Control Unit (DCU) / SCR control module: DEF/AdBlue quality sensor internal failure (short circuit to battery error)

The control module has detected that the voltage on the DEF quality sensor circuit is abnormally high, matching battery voltage. This typically points to an internal short circuit within the sensor itself, or a short to battery power in the wiring harness. Because of this short, the sensor is unable to accurately measure the DEF/AdBlue concentration and temperature, which will likely induce an engine derate or power loss.

• MAXXUM T4E
• Case IH 240 Series Axial-Flow Combines
• Case IH Magnum and Steiger Tier 4 Tractors

1. 1

   Inspect the wiring harness and connectors between the DEF quality sensor and the ECM/DCU for chafed wires, melted insulation, or pinched harnesses that could cause a short to battery power.

2. 2

   Disconnect the DEF quality sensor, turn the key ON, and measure voltage on the sensor signal pins. If battery voltage is present, the harness has a short. If a 5V reference is present, the short is internal to the sensor.

3. 3

   Ensure the latest engine and aftertreatment (DCU) software is installed, as updates can address false sensor faults.

4. 4

   Test the DEF fluid with a refractometer and test strips to ensure the tank is not contaminated with diesel or water, which can foul the sensor probes.

1. 1

   Prepare machine

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical spikes during the repair.

2. 2

   Clean the area

   Locate the DEF tank and thoroughly clean the area around the DEF head unit/quality sensor mounting flange to prevent dirt or debris from falling into the DEF tank.

3. 3

   Disconnect components

   Disconnect the electrical connector from the DEF quality sensor. Carefully disconnect the DEF fluid supply and return lines (be prepared to catch minor fluid spills).

4. 4

   Remove the sensor

   Remove the mounting bolts or retaining ring securing the DEF quality sensor/head unit to the top of the DEF tank.

5. 5

   Extraction

   Carefully pull the old DEF quality sensor assembly straight up and out of the tank.

6. 6

   Install new sensor

   Insert the new OEM DEF quality sensor assembly into the tank, ensuring the sealing gasket or O-ring is properly seated.

7. 7

   Reassembly

   Tighten the mounting hardware to the manufacturer's specified torque. Reconnect the DEF fluid lines and the electrical connector.

8. 8

   Clear codes and test

   Reconnect the battery. Connect a diagnostic scan tool to the machine, clear the active 19153 (624E) fault code, and run the engine to verify the code does not return and the DEF system is dosing properly.