88 s10 check engine light inoperative

I have an 88 s10 2wd 2.5l. When i have the Key On Engine Off, the check engine light will come on for a split second then go off (which i think is normal). But when i try to jump the A and B terminals in the Data Link Connector in order to set the timing, the light doesnt come on at all. the truck runs and drives fine..just a little on the rich side. Was wonderin if anyone ran into this problem before and could possibly point me in the right direction. Dont really wanna play the wire tracing game more than i have to ( which im thinking its a ground problem). Any help would be great thanks.

It should at least come on when you turn the ignition to 'on' without starting it. It is faulty if it doesn't. It mat be possible for a loose ground to cause that, but my Dad's first suggestion when troubleshooting is a loose ground. I cant remember him ever being right. My 88 S-15 has the same motor, 350,000 mi. and never had that particular problem. I cant check my manual either because im outta state workin. I wouldn't complain too much though- usually people cant get them to go off, not come on. :biggrin: