Workshop questions

I bought a GEBE NOx sensor from you. Unfortunately, I couldn’t remove the old sensor head from the exhaust, so I cut off the cable and soldered it to your new NOx control unit. Why isn’t the sensor working now?

I own a Mercedes-Benz A-Class that was registered in September 2018. The NOx sensor A 000 905 31 09 was originally installed. I have now fitted the GEBE sensor 9 2968 1 from you, which corresponds to this part number. However, the car reports that the sensor cannot be calibrated because it has the wrong part number. What am I doing wrong?

Answer: The NOx sensors for this vehicle have been successively updated by the manufacturer. The replacement sequence is as follows:
A0009053109 (GEBE 9 2968 1) → A0009058111 (GEBE 9 2997 1) → A0009051014 (GEBE 9 3685 1).
Due to product improvements and/or software updates, it is likely that the vehicle’s ECU now only accepts the latest version.
We recommend using the GEBE sensor 9 3685 1, which corresponds to A0009051014. This version will be recognized by the vehicle without any compatibility issues.

The engine light comes on in my SEAT Alhambra 2.0 TDI 4Drive from 2013. The following error is stored in the engine control unit: P220B – NOx Sensor 2 Supply.
This indicates a fault in the second NOx sensor. However, I can only find one NOx sensor in my car. Where is the other faulty sensor supposed to be installed?

Answer: Modern NOx sensors are based on broadband lambda sensor technology. Some manufacturers classify certain lambda sensors as NOx sensors.
In your vehicle, a broadband lambda sensor is installed in position 1, and the actual NOx sensor is installed in position 2. This is why the engine control unit refers to the NOx sensor as “Sensor 2” — the first position is occupied by the lambda sensor, which is not a true NOx sensor but is functionally related.