service engine soon light

i recently had auto zone check my 92 grand am because the service engine soon light was on. they said the o2 sensor was bad. so i bought a new one and replaced it. we disconnected the battery to reset the computer, but it is still on. it comes on when i start the car and stays on for about 15 minutes then usually goes off. sometimes it doesnt even come on. what is the problem. and does anyone know exactly how i can diagnose the car my self, i heard of people using a paper clip or something. please help me.

dunno if this will help you or not...http://forums.s-series.org/viewtopic.php?t=15991

does anyone know exactly how i can diagnose the car my self, i heard of people using a paper clip or something. please help me.

I don't know about the later model GM's, but I used to use a paper clip to short 2 connectors on my 88 Olds Cutlass when the check engine light would come on ... the stored code(s) would then blink via the check engine light and I could look them up using my mechanic's tech manual ... he warned me to NOT try this method with my 99 GA/SE though ....

I don't know about the later model GM's, but I used to use a paper clip to short 2 connectors on my 88 Olds Cutlass when the check engine light would come on ... the stored code(s) would then blink via the check engine light and I could look them up using my mechanic's tech manual ... he warned me to NOT try this method with my 99 GA/SE though ....Yeah you cant use that method on the OBDII computers I think its 96 up vehicles but I know for sure 97 and up,you need a scanner tool for those types..I just run to AutoBone(Zone) to get my 97 grand am checked