There are no codes. The E-light on the early MJs is on a mechanical timer set to go off after about 80k miles. It does not mean that there is anything wrong with the truck.
The timer is a small clear box under the dash. Just unplug it and forget about it. Unless you live in a state that requires you to maintain it, then you need to get a new one at the dealership.
-88 MJ; 4.0L, ex-2wd, TJ ax15/231, 78 Ford D44 w/spool, 9" w/posi, 33" trXus MTs, custom roll-bar/bumpers/etc.
Also an 86 MJ Metric ton and 2 '90 MJs
Projects/wheelin' pics: picturetrail.com/petermontie
My email: firstname.lastname@example.org