BMW AUC Sensor Fault Reset: Step-by-Step Procedure

The AUC sensor, also known as the Air Quality Sensor, monitors pollutants in the outside air and automatically controls the air recirculation function of the climate-control system.

Switch off the ignition.
Park the vehicle safely and turn off all electrical systems.
Inspect the AUC sensor.
Check the sensor connector, wiring, and surrounding area for corrosion, moisture, loose connections, or physical damage. The sensor is usually located near the engine-bay air intake or radiator area, depending on the BMW model.
Repair the fault before resetting it.
Reconnect any loose plugs, repair damaged wiring, or replace the AUC sensor if it is defective. Clearing the fault code without fixing the cause may result in the fault returning.
Connect a compatible diagnostic scanner.
Connect BMW ISTA, INPA, or another BMW-compatible OBD diagnostic tool to the vehicle’s diagnostic port.
Turn on the ignition.
Switch the ignition on without starting the engine.
Access the climate-control module.
BMW AUC Sensor Fault Reset: In the diagnostic software, select the IHKA module, which controls the heating and air-conditioning system.
Read the fault codes.
Check for AUC-sensor-related codes, such as an open circuit, short circuit, implausible signal, or communication fault.
Clear the fault memory.
After confirming that the sensor and wiring are functioning correctly, select “Clear Fault Codes” or “Delete Fault Memory.”
Cycle the ignition.
Turn the ignition off, wait approximately 30 seconds, and then restart the vehicle.
Perform a final check.
Scan the IHKA module again and confirm that the AUC sensor fault does not return. Test the automatic air-recirculation function to verify correct operation.

Important Note

Disconnecting the battery normally does not permanently reset an active AUC sensor fault. The underlying electrical or sensor problem must be repaired, and the fault memory should then be cleared with a suitable BMW diagnostic tool.