Jeep: '96 grand cherokee question

Dear collective brain,

I'm the original owner of a 1996 grand cherokee and the car has about
130,000 miles on it. The "check engine" light goes on sporadically. My
trustworthy mechanic says it happens to these cars; he can't find
anything wrong except the light itself. Any advice on how to fix it?
(besides cutting the wires to the light. ha ha.)

thanks,
David Newton

David Newton proclaimed:
 

No. That does not just happen. Find a mechanic that can spell
"Jeep" and knows how to pull codes. The 96 should work with the
ignition key trick, so you might want to start there.

By any chance, are you using an aftermarket gas cap? Or yours is
deteriorated?