2010 Q7 TDI - AdBlue level adaptation (and others) missing

[Uwe]

higher downstream readings.

That's implausible. I could see them being the same if the SCR cat and Adblue aren't doing anything, but the downstream can't be higher than the upstream because there's no conceivable means for there to be more NOx after the SCR cat than before it.

-Uwe-

 

[SaVAGeSoot]

That's implausible. I could see them being the same if the SCR cat and Adblue aren't doing anything, but the downstream can't be higher than the upstream because there's no conceivable means for there to be more NOx after the SCR cat than before it.

-Uwe-

I'd guess the el cheapo sensor might be a factor

 

[5280-Audi-AQ]

I'd guess the el cheapo sensor might be a factor

I fully agree and swapped the cheapos for the expensive Audi ones and still got a downstream reading higher than the upstream. I don’t have a scan to share since I gave up and sent the car to a shop.

 

[SaVAGeSoot]

Once could only apply logic and suspect the upstream sensor had gone wacky in that case....

 

[5280-Audi-AQ]

Once could only apply logic and suspect the upstream sensor had gone wacky in that case....

I thought so too so I replaced both with brand new ones.

I should also mention that the readings aren’t always higher downstream than upstream. There’s obviously a lag as the exhaust gases move through but it always seems like the downstream takes longer than expected to return to the expected values.