AUC II Sensor
The AUC II sensor is controlled and powered by the junction box. The 
junction box
collects the data from the AUC II sensor and transfers it to the IHKA 
control module via
the K-CAN where the data is then processed.
The AUC sensor has the ability to detect:
• Carbon Monoxide (CO)
• Hydrocarbons (HC)
• Oxides of Nitrogen (NOX gasses).
The AUC II sensor is mounted in the IHKA filter housing on the bulkhead.

Air-recirculation Mode
In air-recirculation mode, the flow of outside air can be stopped to prevent 
pollution
from entering the vehicle, e.g. in traffic congestion. Air inside the 
vehicle is continually
recirculated.
To make sure that there is a sufficient supply of fresh air, 
air-recirculation mode is only
available for a limited time (30 minutes air recirculation -> 30 seconds 
partial fresh air ->
30 minutes air recirculation -> etc.)

Automatic Air-recirculation Control
If the AUC II sensor detects an increased level of pollutants in the 
environment from
spark-ignition and diesel engines, the IHKA control unit will automatically 
switch to airrecirculation
mode.
To make sure there is still an adequate supply of fresh air, air 
recirculation is only
available for a limited time:
• At ambient temperatures less than 0°C:
2 minute recirculated air mode -> 20 seconds fresh air mode -> 2 minute
recirculated air mode -> etc.
• At ambient temperatures from 0°C to 6°C:
3 minute recirculated air mode -> 20 seconds fresh air mode -> 3 minute
recirculated air mode -> etc.
• Operation without a/c function at ambient temperatures greater than 6°C:
4 minute recirculated air mode -> 20 seconds fresh air mode -> 4 minute
recirculated air mode -> etc.
• Operation with a/c function at ambient temperatures greater than 6°C:
12 minute recirculated air mode -> 20 seconds fresh air mode -> 12 minute
recirculated air mode -> etc.
When the engine is started and the AUC function activated, fresh-air mode is 
always
selected for approx. 40 seconds due to the warming phase of the AUC sensor.