Code pulling problems...

[squeals99]

alright well as i am going down the highway, traveling at constant speeds around 75ish... but it will do it at 55-upward as long as it is going at a constant speed most of the time, but my check engine light comes on for about 20 seconds and goes back off, and it does this periodically.... and so my question is... well first of all my car is a 94 formula... but so anyway... i was told that the only time the codes can be pulled from the car is when the ignition is in the on position, but not when the car is running... and i was also told that the only time a code can be pulled is when the SES light is on, and if it isnt on then it will not throw a code... so my question is... can i hook up a scanner to it and drive it till it throws the SES light, and then will the code show on there? or would it hurt anything to try doing this?

i am thinking it is an o2 sensor, but i just want to make sure it is before i go buying out the ass for parts and end up never figuring out my problem... and i was also told that the stock cat on my car has a small hole in it... why? no idea, but my guess is possibly that it was hollowed out and not sealed back... but i have never seen the hole, and i plan on replacing the cat with my friends's old stock cat from his 04 gto.... but i would like to know what i am throwin before i start shootin parts into it

[2001NBMZ28]

Don't know how long codes are stored as "history" for OBDI, but most OBDII codes stay there for 40 ignition cycles after the light goes off. If you know someone with an OBDI scanner I'd try and read the code.

[squeals99]

well ya i do know someone that has one... my buddies dad owns a muffler shop and has one... but i just wasnt sure how long that code would stay stored...

[Ryans99LS1]

Wouldnt worry about it untill the code actually sticks and the light stays on. Unless you feel like your car is running worse. IRC there should still be a record of what codes your car has thrown, regardless of whether or not the light is still on, so just try and pull them anyway.

[squeals99]

k well it is runnin sorta bad... it misses toward the top end a little bit and runs crazy rich sometimes, so i guess i will just try to pull some codes this weekend and see if i cant get the right codes or see whats goin on exactly....
but im guessin an o2 is bad, and my cat is probably bad because of this too