I own a 2002 A6 3.0. I have the CEL on with code P0050 (HO2S bank 2, sensor 1). I believe this indicates the oxygen sensor upstream from the cat on the driver's side. The sensor is on the exhaust manifold, and appears to be very hard to access. The brake fluid reservoir, and a lot of other stuff, is in the way. Any advice on how to get to this sensor to remove it? From above, or from underneath the car? Any special tools required, besides an O2 sensor removal socket?

Thanks. Brian

 

If it is bad, don't overlook the wheel well as a possible means of access. And don't twist the hell out of the wires on the new one when you install it.

Good luck.

 

I know this is an old post, but I just replaced a B2S1 in my 3.0l and wanted to share my experience to save others time on this somewhat complex repair. It wasn't fun. I couldn't see anyway to do it from above. It looks tempting, because you can barely see the sensor, but no way to reach it with a tool and definitely no leverage. I followed another's advice and removed the driver's side axle. I can't see how you could do it without removing the axle. I bought the oxy sensor wrench from Autozone; I don't see how the socket oxy sensor tool would work for this one. Once you get the axle out, it's much easier to get in and up to the sensor. Now I have a kwik lift so access was decent. There is also a sensor with a bracket on the subframe that is in the way for gaining leverage with the wrench. One 6mil hex and the bracket comes off enabling you to get good leverage for removal and installation. Total time about 2 hrs., and it was handy to have a helper (and kwiklift).
Note: I've finally made friends with the dreaded pinch bolt. I now use MAPP gas and heat the area around the bolt. Then I use an impact wrench to turn the head of the bolt after it was heated. (Don't be bashful with the gas, at least 1-2 min of direct heat. Pprotect the upper link boots with a scrap piece of metal while heating - I used an old license plate.) I've done two pinch bolts like this recently and it went much easier than ever before. Probably a good idea to clean out the hole after removing the bolt.
Jim
'03 A6 Avant

 

I HAVE 2004 A6 3.0, I TOOK A COUPLE OF PARTS FROM THE FIREWALL ON THE OTHER SIDE OF THE ENGINE. WITH A LONG EXTENTION, UNIVERSAL JOINT,02 SENSOR SOCKET AND RATCHET. PUT THE SOCKET ON FROM THE BOTTOM GUIDE THE EXTENTION DOWN TO THE SOCKET , USE BOTH HANDS TO PUT SOCKET AND UNIVERSAL TOGETHER. TOOK ME ABOUT AN HOUR TO CHANGE BOTH FRONT SENSORS.