Check engine connector problem

My 1991 2.3L Mustang has an occasional check engine light. I want to read the codes but the connector does not have a jumper wire to connect to the test pin. I tried grounding the pin but with key on engine off but the check engine light just stayed on (no blinks). Any help?

Thanks

Here is a link to a Site the lists the trouble codes as well as the diagram to hook up self test jumper to read your codes. Auto zone will read the codes for free but it pays to know how to do it. you will need a volt ohm meter to test your vehice with this method. Good luck!! post your progress and let us know how you make out and if you need anymore help!!

http://autorepair.about.com/library/ts/obd-i/bl-dtcs-98.htm

Thanks for the link. I found the Self Test input and connected it to ground on the Data Link Connector . Then I turned the ignition on, engine off. I waited to see the check engine flash but it simply remained illuminated. my understanding is that you should be able to count the blinks.

I noticed that while driving the check engine goes on for a few minutes occasionally and then goes out. I also noticed that when thgis happens the tach starts jumping around but the engine is not surging nor running differently. Does the tach get its info from the crank position sensor? The problem is not noticeable except from the check engine light and flakey tach, should I just ignore it?

If I am not mistaken autozone by me will only pull codes on OBDII compliant cars (generally 1996 and later) and not OBDI (before 1996).

Thanks