Hi would you have the three photo as I am having problem with post cat sensor I think thank youRight, after a sudden rush of blood to the head (see my PM Giles - you of course have the FSI, there aren't any NOX senders on 1.4 petrol cars, doh!), I've got to the bottom of the NOX issue - I think!
I've attached 3 photos, showing firstly the wiring between the sender, the control unit and the ECU and then 2 diagrams showing the locations of the parts involved (to orientate yourself, the NOX sender diagram shows the underside of the car and the exhaust pipe, the control unit diagram is showing the passenger footwell compartment).
As you will see, there is ONLY 1 NOX SENDER.
Also, the wiring all leads back to the ECU, so it could well have been a faulty ECU to start with. I know exactly what the dealers have done - they started by replacing the least expensive part (the sender), then when this didn't work, they moved on to a more expensive part, and now finally, they're going for the daddy, in cost terms - the ECU.
They did this with my power steering faults - firstly doing absolutely jack, then going for the fuse, then finally having to bite the bullet and replace the controller.
So, I would surmise that in fact your ECU was faulty from the start and that as the fault occurred within warranty, it should be repaced free of charge, even though the car is now technically out of warranty.
Just imagine - your gearbox was playing up and you booked it in to have it looked at only to be told that they couldn't fit you in for a fortnight, when your warranty has 10 days to run - would you expect to stump up for the parts? I wouldn't and I don't think you would either.
Say no to any 'goodwill' gesture, you're entitled to have this fault rectified free of charge - it's not your fault that the dealer couldn;t get to the root of the problem in time is it?
Hope this helps,
Number 3 is the second CAT on the FSI. Its a spectial NOx storage catalytic converter which is unique to the FSI. When running in lean burn mode, the engine produces lots of NOx gasses and these are captured in the storage catalytic converter. When this is "full", the engine switches mode and the stored NOx is converted into nitrogen to be released out the exhaust. The NOx sensor is used to detect when the converter is "full" so is required for proper operation of the engine. If the NOx sensor isn't working then the engine will never go into lean burn mode and fuel consumption will be higher.Thanks Skipton01 really useful I guess the part number 3 is a dpf? as there are two number 20's. With the 1.6 fsi I guess only the two as I have not yet ventured under the car. WIth the scan I am getting NaN% reading for the bank 1 sensor 2, I did a temperature test of the cat seems to be working but has P0139 code cheers Andy