Hi all ,new to this forum. I have 2 fault codes PO411 (secondary air injection/incorrect flow) and the 02 fault. Where are the O2 sensors located and what vacumn lines do I need tocheck? Thanks for any help. Mike

 

you have a primary o2 and a downstream o2. The easiest one to spot is on your downpipe.. Just pull back your heatshields and you will see it. The other is after your cat.

 

specs of your car?

 

Agreed - we need to know year, model, engine, drivetrain, and transmission. Not all of those apply to your current question, but they'll help in the future. Go to your profile page, make a signature, and include that information, and it'll save a lot of time in the future. See mine below - that'll give you an idea of what Hiwords and I are talking about.

 

Wow Thanks for the posts. I will do profile

 

For now A41.8 L Quattro autotrans. I ordered O2 sensors from onlineautoparts (Ebay seller)