First off gotta say this is a nice board for info.

To the point, posting for my cousin, she a has a 2003 audi a6. Codes were checked and P0171 & P0174 came up, so the o2 sensors gotta be replaced. Car is a tad over 90k miles so makes sense. My question and maybe I'm just a tad slow today, but how many oxygen sensors do these cars have? I just want to make sure its a total of 4, 2 upfront and 2 to the rear. Other question would be, how hard to replace?

Thank you for any feedback.

 

Ok little more scrolling around, 4 should have been obvious. Drivers side seems to be the hard one, still trying to find a write up, passenger side looks decently easy. Since rear ones are under the car, assuming they aren't too hard either.

 

http://forums.audiworld.com/showthread.php?t=2775139

^^ BOOM!

hope that helps, was just posted yesterday.

 

Yep, that definitely looks like it will help a bunch. Also makes it seem like a nice PITA.