NOX sensor issues P220A00


New Member
Jul 31, 2021
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Hello all,

Looking for some advice regarding NOX sensor issues that have been ongoing in my 2016 Audi A7. Essentially there was a historic code cleared for NOX sensors last year that an independent Audi garage done for me when my car was in for a coolant leak. I had noticed that the fuel economy was dwindling and was told that the NOX sensors have no relation to this.

Continued on eventually an EML came on the dash, again for NOX sensors. By this point I had notice a rough idle from cold that lasts about 10-15 seconds and then goes away. Nothing else was affected and the car drives as normal.

So I got an OBD 11 device, cleared the codes and eventually replaced both NOX sensors, as both codes had come up, with genuine audi sensors (£877 each!).

Everything was fine, rough idle gone and fuel economy had improved slightly but still wasn't back to normal. About 2 weeks later rough idle returned and so did the codes.

I have taken the car back to the independent audi garage and all they've done is cleared the codes and told me there is nothing else they can do as everything looks fine with the car.

I find it very hard to believe that this brand new NOX sensor is immediately inoperative after 2 weeks.

I have done loads of research with many conflicting reports. Some say a NOX sensor is a plug and play, others say I need to reset parameters or update software. I called Audi Hamilton, which is my local audi dealer who were more interested in charging me £140 for a diagnostic check but eventually confirmed that no coding or updates are required ECU wise and it should be a plug and play.

Alot of info suggests a correlation between NOX and adblue but I have had no issues in that regard.

The main sysmpton I have is a decrease in fuel consumption. Could only manage 42 mpg on a recent trip to York, about 210 miles of motorway driving which is well below what I've had before. Used to get 450ish miles from a full tank of mixed spirited and conservative driving and now I struggle to get close to 400 miles whilst constantly trying to drive with fuel economy in mind.

My main question is what do I need to do to get this back to normal? Is there something I can do with OBD11 to kick-start the NOX sensor into normal readings?

My ability with the OBD is limited, I have looked at the readings for the NOX and it means nothing to me. The code displayed is the one above P220A00 - NOX Sensor supply voltage bank 1 sensor 1.

Any help would be greatly appreciated.


Car - 2016 Audi A7 Black edition, 3 litre TDI 218bhp CZVA engine, 63000 miles, serviced every year.