xlilmama10211x

So my 2001 Audi A6 2.8 Quattro has a CEL on for p0140 and p0136 both indicating an issue with my Bank 1 Sensor 2 o2 sensor. These lights came on after having my coolant temp sensor changed, new coil packs and plugs, a new valve cover gasket for an oil leak I had forever, and other non-engine related things. Car has a slight stumble upon starting as well as a subtle shake or vibration in idle. Acceleration has been poor as well. Occasionally I will smell sulfur when accelerating onto the highway, but this comes and goes. So those are the details on its condition..
I am trying to change the B1S2 on this car, and downloaded an Audi repair manual from Autozone that has a diagram of the exhaust system, but its very confusing.

It says there are THREE o2 sensors on bank 1:
--B1S1-pre-cat
--B1S2-pre-cat (right before it)
--B1S3-post-cat

and than ONE on bank 2:
B1S1

Which sensor am I changing? The passenger side o2 sensor right before the cat, right? Everything I've seen online says that the 2nd sensor is always after the cat...

Any advice on possible issues or how to replace this o2 sensor is greatly appreciated!!! Thanks

clancy

two on each side: B1S1, B1S2, B2S1 & B2S2. Post cat means the short cat not the long one.

I see you are new to this forum. The search function is your best resource. There are many posts one replacing these. It does take some time to learn how to use the search effectively but well worth the time invested. Hint, click on search then advanced. This allows you to narrow to just C5 or whichever.

https://www.audiworld.com/forums/a6-...uting-2895300/ This will get you started. Then click on
https://www.audiworld.com/forums/a6-...ested-2775139/ This one is for the front ones, B1S1 & B2S1 but well worth reading