I have a 96 SE mtx and keep getting these bad o2 sensor codes. The Haynes manual says there are two o2 sensors but as I keep reading in these forums, there appears to be 4. SI went to autozone to buy a sensor for the front and it had a square clip instead of round. Could this possibly go to one of the other two sensors I cant find or it is the wrong part. If there are 4 where are the two upper ones? Hate to keep beating a dead horse asking the same questions, but a lot of the links here don't seem to work.