Can somebody give me a detailed walkthrough of how to get codes from a 90 civic CX? My GF says she keeps getting CEL's, although infrequently... I figure it's an O2 sensor, but who knows... I wanna check.

Any help is appreciated.
I've already searched! But have only found out that you can use the paperclip, not HOW to use it.

 

its obd0...the ecu is under the carpet in the passenger side floor board...pull the carpet back and when u turn the key on u will see a little red led flash...1 flash means the igniton is on and anything after that is a code...count the flashs and then come back and look for the codes...

 

whoa, so no paperclip is required? obd0 pwns.