wow there is only a 3 pin connector on a 91 geo storm is there a adapter for my scan tool that reads a 12 pin aldl thanks steve

 

You just need to jumper the 3 pin connector and count the flashes on the check engine light.


To get the check engine codes to flash in your dash panel, use a jumper wire or a paper clip and connect terminals A and B of the diagnostic connector. Turn your ignition key on with engine off and the codes should start to blink. All codes should start with code 12 which is one long flash followed by 2 short flashes. This code 12 means the diagnostic system is normal and will repeat itself continuously if there are no trouble codes. Otherwise, code 12 will flash 3 times before flashing the fault codes.

 

And here's some help:

http://www.troublecodes.net/GMimport/91geo16.shtml