Hiya folks

 

Could do with a little help if possible please. I have a few faults I'm trying to resolve: car is a 2017 2.0tdi A4, B9

- The first is a P2200 NOx sensor fault.... I understand this to be (perhaps incorrectly) the engine side sensor but have read and watched a video somewhere that suggests this code is post sensor. I've used live data in VCDS and appear to be getting a PPM reading engine side and can't get another reading from any of the other options for post. But then again figured thats what SCR is meant to do and ensure NOX becomes N and O2? I have a sensor coming and think other than slight differences to loom they may be the same sensor for both positions. BUT where the hell is the engine side sensor?

- Also code P06DA - oil pressure circuit, assume this is a faulty solenoid but like above I can;t find it anywhere...

Edit - also any NOx sensor learning/coding to required?

Any help appreciated folks...

 

Edited August 20, 2025Aug 20 by bantamdave21
Addition of coding ?

9 hours ago, bantamdave21 said:

Hiya folks

 

Could do with a little help if possible please. I have a few faults I'm trying to resolve: car is a 2017 2.0tdi A4, B9

- The first is a P2200 NOx sensor fault.... I understand this to be (perhaps incorrectly) the engine side sensor but have read and watched a video somewhere that suggests this code is post sensor. I've used live data in VCDS and appear to be getting a PPM reading engine side and can't get another reading from any of the other options for post. But then again figured thats what SCR is meant to do and ensure NOX becomes N and O2? I have a sensor coming and think other than slight differences to loom they may be the same sensor for both positions. BUT where the hell is the engine side sensor?

- Also code P06DA - oil pressure circuit, assume this is a faulty solenoid but like above I can;t find it anywhere...

Edit - also any NOx sensor learning/coding to required?

Any help appreciated folks...

 

Hi one of the sensors is in the group of sensors  pre cat the other sensor will be post DPF the idea being the first sensor reports nox level to the ECU which then starts Adblue injection, the secondary sensor reports that the nox levels are still to high so the ECU pushes up the level of Adblue to compensate, downstream sensors are slightly different from upstream in build as the sampling core is different to account for the Adblue in the stream, generally speaking the downstream fails first as it has a harder life, both sensors should have different coloured plugs/ part numbers which denote upstream/downstream but if as you say the part numbers are the same you should be ok.

Steve

Thanks Steve

Is there a normal range of readings at all? As I’m getting zero ppm post cat I’m assuming the issue is there? I know the adblue aims to reduce nox but assuming zero ppm isn’t realistic too….

cheers

Dave

10 hours ago, bantamdave21 said:

Thanks Steve

Is there a normal range of readings at all? As I’m getting zero ppm post cat I’m assuming the issue is there? I know the adblue aims to reduce nox but assuming zero ppm isn’t realistic too….

cheers

Dave

Hi zero ppm is impossible, if you get a reading on the first sensor its working ok, but you for example are getting say sixty on the first sensor it should translate to ten down stream and then reduce as the extra adblue kicks in but in any case it will never reach perfect zero that only ever happens on cars post 2020 that have a further adblue injector in the pipe way after the DPF and then registers zero at the end of the tail pipe, there are no average or normal readings as each engine and its operation are unique, its only Euro 6 engines that have two nox sensors Euro 5 only have one in most cases.

Steve.