Going to replace the upper o2 sensor today, can anyone post a picture or explain where exactly its at?

 

I can't remember which is which, but I know one O2 sensor was in the y-pipe, about where it bolts up to the manifold (I think that was the drivers side) and the other one (probably passenger side) was actually in the manifold. Just get under the car with a flashlight and look to where the y-pipe meets the manifold.

 

Okay, i crawled under the car and found a o2 sensor directly in front of the oil filter. Would this be the upper? i cant seem to find the other one. Any idea?

 

I don't know where you got the idea of upper and lower, they usually go by left bank (driver side) and right bank (passenger side). So if its near the oil filter, you've located the driver's side. Now look at about the same height on the other side of the motor, and you'll see the other one. Hope this helps you out.

 

Okay i found the other one. they are both at the bottom of the headers where the header meets the Y pipe. Now a new question. The one closer to the driver side tire looks alot thinner then the other one. Is that normal? they both have the flat 4 pin connector.

 

No, they should be the same size. One of them may be stock and the other one aftermarket or something like that. Either way, I wouldn't worry about it. Its not a big deal.

 

For stuff like this, its always a good idea to start with Shoebox's Tech Pages....

http://shbox.com/1/4th_gen_tech1.html

http://shbox.com/1/ho2.jpg