4Driver4

Please edit your subject lines. My mouse is low on clicks and I hate to waste them. Thx.

win_r6_02

I looked underneath the car and tapped on the Cat and it didn't rattle. I noticed that there's only one O2 sensor for each Cat. On the driver side, the O2 sensor is somewhat mounted sideways (right side of the Cat if your lying down facing towards the front end) and on the passenger side is mounted on the top of the Cat.

thank you for your insights...

4Driver4

There are four oxygen sensors. You just can't see the others.

win_r6_02

would you happen to know how to check the voltage reading on an O2 sensor and what it should be reading.

Ernesto (ERT)

Find yourself friendly tuner shop who will help you diagnose the issue. Mine replaced the O2 sensors, and said if the exact same codes came up they would put my old one's and go to the next step/option.

4Driver4

Efficiency is calculated based on the delta between S1 (front) and S2 (rear) sensor. The best test is to swap the B1 and B2 rear sensors and see if the problem moves.

win_r6_02

I found few pictures from Autozone's website. It shows where the O2 sensors are located.

One O2 sensor (passenger side) is located near the head gasket area mounted right after the the exhaust manifold under the hood. The other O2 sensor (passenger side) is underneath the car right before the cat. Please correct me if I'm wrong.

I might tackle replacing the the O2 sensor first than the cat...don't know which one yet...but, it's the cheapiest route...

thanks

4Driver4

Not the approach I would take.

Imola a4

you can try swapping o2s but id say if you can pull up a vag com on any decent scanner and see how your pre and post o2s are switching on a graph if their about the same then your cats most likely bad