O2 Sensors

I have a manual for my 96 Max it says that there are 3 sensors(two up stream and one down stream) but I can only locate to of them. Have any of you guys ever changed out these pieces and where can I find the third one?

I don't have a 96 but I am almost certain that there is two in the y-pipe, and one in the cat. My 99 has one after the cat. The one's in the y-pipe are hard to get to but they are there.

I have a '95 and the o2 sensors are: one in each exhaust manifold about 6 inches from the block.(one can be seen down in front of the rad. the other is in the rear of the engine bay you might be able to see it.) the third is under the car near the shifter in the y-pipe.

:D Can anyone supply a pic of where the "front" O2 sensor is? I just ordered a new sensor to replace the old. I was hoping to get some help instead of forking the money to get a service manual for this. Thanks a bunch! :D