Deutz-Fahr 1138 – ECM or DCU: AdBlue Tank Temperature Sensor Error

The Engine Control Unit (ECU) has detected that the signal from the DEF tank temperature sensor is outside of its expected operational range (either above the maximum or below the minimum limit). This typically indicates an electrical failure, such as a short or open circuit in the sensor's wiring, or a complete failure of the sensor itself. Accurate temperature readings are critical for the ECU to control the DEF heater and ensure the fluid remains in a liquid state for proper dosing into the exhaust stream.

• TCD Series

1. 1

   Verify AdBlue (DEF) quality and level. Ensure the tank is filled with fresh, high-quality DEF meeting ISO 22241 standards and check for discoloration.

2. 2

   Inspect the AdBlue tank, lines, and injector nozzle for white crystal deposits, which can block lines and interfere with sensor readings.

3. 3

   Check the electrical connectors and wiring harness leading to the AdBlue tank sensor for signs of damage, corrosion, loose connections, or chafing against the chassis.

4. 4

   Test the sensor signal using a diagnostic tool to read live data and compare it to ambient temperature for plausibility, or use a multimeter to test the sensor's resistance/voltage output.

5. 5

   Check for other active or stored fault codes related to the SCR system (e.g., NOx sensors, AdBlue pressure, or dosing module performance) that might trigger a temperature sensor fault.

1. 1

   Address preliminary issues

   If diagnostic checks reveal poor DEF quality, crystallization, or wiring damage, rectify these first. This may involve draining and flushing the AdBlue tank, cleaning components with deionized water, or repairing the wiring harness.

2. 2

   Replace sensor assembly

   If the sensor is faulty, drain the AdBlue tank and disconnect the electrical connector and attached lines. Remove the old sensor assembly, install the new one ensuring a proper seal, reconnect lines and wiring, and refill with fresh AdBlue.

3. 3

   Clear codes and reset system

   Use a compatible diagnostic tool to clear all fault codes from the ECM/DCU. Perform any required adaptation or recalibration procedures so the system recognizes the new sensor.

4. 4

   Run a drive cycle

   Operate the machine to allow the SCR system to perform a self-check and verify that the fault code does not return.