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Jeep "Check Engine" light

I am having a “Check Engine” light problem on a stock 06, 4 cylinder Jeep Wrangler with manual transmission. A local highly regarded independent mechanic has had it in his shop 3 or 4 times for more than a day each time. On the first visit he replaced a purge solenoid valve and reset the light. It stayed off for more than 400 miles and then relit. He went over it and checked the wires and connections and reset the light. Again it stayed off for some time and then relit. He has checked the Jeep site and tried the suggestions there. He now refers to this as a ghost. After the last visit he suggested I drive it and see if it would reset itself as it had been doing in the past. It did reset itself twice but it only stayed off for 10 miles the first time and 2 the second. The code indicates an electrical problem and he is now planning to drop the fuel tank and check the wires and sensors there. The next step may be an ECM transplant.
Do you have any suggestions to try for a fix?
This is only an emission system problem and the mechanic says it is OK to drive. We do not have emission inspections here. How important is it to fix the problem?

Post the code here is probably the first thing to do. Some folks who participate here know how to interpret these codes and can come up w/some experiments to try.

It sounds like it is some kind of fuel tank venting problem. Sometimes this is as simple as a gas cap that is leaking and venting gas vapors. I guess if this were my car the first thing I’d try – given what you say – is to simply replace the gas cap with a new one. Or I might simply rub a thin coating of oil on the existing gas cap’s rubber seal to make it seal better. Then I’d drive the car a while and see if that reset the light.

I understand this is frustrating to you. This is actually a problem that shouldn’t happen in an ideal world. Not that something breaks. That’s bound to happen. But that it breakes and you haven’t a clue why. First thing, the check engine light codes should be available to the car owner by simply reading a display on the dashboard, or counting a series of check engine light flashes, etc. That would be simple to implement. Second, once the code was read, the manufacturer’s web site should provide an perfectly understandable explanation (for the layman) what exactly the code means. What sequence of events must be detected for the code to be set, etc. And it should give the owner the possible causes, in order of most likely to least likely.

But this as you understand isn’t an ideal world. I expect the reason is that the manufacturer wants you to use the dealership shop for repairs, as this is extra income for the dealership. And there are probably some technical reasons. And there may be safety and liability reasons why the manufacturer doesn’t want to provide this info.

One thing you could do. Next time ou purchase a car – ask the salesman to show you how to read the codes on the car you might buy, and the website that would be available to you to show you how to diagnose what is causing the codes to be set. If the salesman can’t do that, look elsewhere for another car.

That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.

Read this post and see if it applies to you.

There are a dozen EVAP/EVR codes…Yours should be listed on your shop’s work order…Please post the codes here…