P1391 cel answer finally!!!
 

Had a CEL for as long as i've owned my 4.0L ZJ. i was getting code P1391. driving me crazy trying to clear it. replaced both sensors. back probed the entire wiring harness. replaced the entire ignition system. Nothing. So after some advice from a seasoned Jeep mech, i replaced the entire distributor. apparently they are prone to wear that is enough to cause the code. It was super easy to do which was nice since i did it in the autozone parking lot to avoid the 75 dollar core charge. the distributor only runs 50 bucks. You will need a phillips head screwdriver to remove the distributor cap and a 1/2" wrench to get the distributor off. Just make sure you pay attention to how the old one comes out and be sure to put the new one in the same way. Long story short, the CEL is finally gone!!! I had searched and searched for the answer to this problem, and from what i can tell NO ONE has tried this to correct the issue. If this works for you, please pass it on to all jeep owners that may have this problem. This would have potential to be a very expensive repair if going at it with no ideas.

Thanks for posting this!:thumbup1: