Check engine--gas related

This one's for my wife's '01 Wrangler 4.0 (no air cond.). She's telling me that her engine light comes on whenever she drops below a half tank of gas. Then, when her low fuel light comes on, no more check engine light. When she fills her up, the light goes off until the cycle starts again. Obviously, it's been doing this for a while, cause she knows the pattern (I'm just learning about it...typical). I'm going to get codes from it the next time the light comes on. Any ideas?

Tell us, how does your wife get the 'check engine' light to go off once it comes on ????? This normally has to go through a cycle (which takes a while) or be reset manually.

Anyways....

Of course, you will have to get the code to find out exactly what the reason the light in coming on (In California you can borrow and OBD reader from Pepboys) in order to be sure but my guess would be that you have a bad gas cap. Gas caps are pressure/vacuum set and the computer will register the lack of such.

The wife isn't doing anything to reset the check engine light. She's just been driving it until the low fuel light comes on, and then when she refuels, the light doesn't come back on until it gets to about half a tank. That's her story and she's sticking to it. The gas cap would be an easy fix.

My guess is that there is a problem with the gas cap. Something similar happened to me when I left the gas cap off at the pump... Once it was back on, and went through it's cycle, the check engine light went off.