Case IH 19165 (DTC 684E) - ECU – Engine Control Unit (ECU) / Aftertreatment Control Module (ACM): DEF/AdBlue Quality Sensor Internal Short Circuit to Battery

The system has detected an internal short circuit to the battery in the temperature source/circuit located within the DEF/AdBlue quality sensor. Because the temperature sensor is integrated into the quality sensor, this internal short compromises the sensor's ability to accurately read the DEF concentration and temperature.

• MAXXUM T4E
• Case IH 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Case IH Magnum
• Case IH Steiger/Quadtrac
• Case IH Maxxum
• Case IH Puma
• Case IH Farmall

1. 1

   Check system voltage to verify the battery and alternator are functioning correctly, as low or erratic voltage can cause false codes.

2. 2

   Trace the wiring harness from the DEF quality sensor to the ECU/ACM, looking for chafed wires shorting to a 12V power source.

3. 3

   Disconnect the DEF quality sensor and inspect the connector pins and terminals for oxidation, corrosion, or pin back-out.

4. 4

   Check for continuity between the ACM and the sensor connector, and measure voltage to ensure it receives the correct 5V reference and is not externally shorted to battery voltage.

5. 5

   If the wiring harness, connectors, and supply voltage test perfectly, confirm the short to battery is internal to the sensor.

1. 1

   Turn off the machine and disconnect the battery.

   This prevents electrical spikes.

2. 2

   Locate the DEF quality sensor.

   Depending on the machine, it is either mounted near the bottom of the DEF tank or integrated into the DEF header unit at the top of the tank.

3. 3

   Disconnect the electrical wiring harness from the sensor.

4. 4

   Remove the sensor.

   If it is a standalone sensor, unthread it from the tank. If it is integrated into the DEF header, you will need to remove the DEF header assembly from the tank.

5. 5

   Install the new DEF quality sensor (or DEF header unit) and secure it.

6. 6

   Reconnect the electrical harness.

   Ensure the connector locks firmly into place.

7. 7

   Reconnect the battery, turn on the ignition, and use a diagnostic scan tool to clear the inactive fault codes.

8. 8

   Run the engine to verify that the SCR system initializes properly.

   Ensure the fault code does not return.