FERM and any other Jeep guys......
 

I have a 99 wrangler 4.0 litre (same motor as the pink Jeep) and the check engine light will not go off, any suggestions. It has been going on and off for the last month on a few days off a week, on again for a few days off a week. Now it is stuck on.

Just put a brand new exhaust manifold on it Sunday. Trying to sell it and need to figure this out. O2 sensor?

Go to Harbor Freight and get a code reader, it's cheaper than making one misdiagnosis.
http://www.harborfreight.com/cpi/cta...emnumber=46030
A lot of things it can be, Chrysler products will have a check engine light on if the gas cap isn't tighened to at least one click.
If you still have problems, holler.

http://www.harborfreight.com/cpi/gifs/clear.gifhttp://www.harborfreight.com/cpi/gifs/clear.gif

so does the code reader come with a book to tell me what the code means? can i get something like this at advance auto?

Yes they come with the book as to what code is supposed to be, also in most repair books there will be a list of the codes. Be sure to cross reference both to see if they transtale to the same thing.
The auto parts store may be a lot more expensive.
If I'm not mistaken Advance may "loan" the reader.
So far the one from Harbor Freight has worked on every Ford and Chrysler products I've stuck it to.

Typically, the check engine light is set to come on after a certain mileage so you will take it to a dealer for an emissions checkout. There is probably nothing wrong with your Jeep.

I had 2 vehicles that did that at exactly certain miles, on one of them the EGR light would come on at exact miles.
After determining there were no problems, I just found the reset, reset them and off for another 10-20,000 miles.
This shouldn't be the case with this one.
Resetting one (now) without a code reader is as simple as disconnecting the battery for 12-24 hours. But the problem will show up again in a week or two if uncorrected.
Allright FERM, get over here!!

That is not the case here, I can assure you. After 92 no chrysler product used a maintence required system on them, and OBDII I believe is mandated NOT to have one. Go to AUTOZONE, they'll check it for you for free. On a 99 you may still be able to get the codes by the old key switch on off on off on off on(some take 3 on's and some take 4) self diagnostic in 2 second intervals and on the last on leave it there. On a 99 the odometer should read out the CHRYSLER HEX code, if it does I got the book to tell you what they are(or you can look them up on line as well). I don't think a 99 TJ will have an LDP, so a loose gas cap is probably not it. If the JEEP is running well with just a check engine light(after a cracked manifold), then chances are that it will be a cat efficiency code or downstream O2 sensor performance code. Only way to know for certain is to get the codes and go from there. CHRYSLER's OBDII is normally pretty spot on, so codes are normally a pretty reliable diagnostic tool.

Our 94 Caravan had the dash diagnostic.
I tried it with a couple of other newer vehicles and they just sat there, but then again, I haven't gotten books on the other vehicles.
Oh, the loose gas cap-check engine light, is the number one thing on the Pacifica.

so FERM, your telling me if i turn the key on and off 3 or 4 times the dash will tell me the code for the problem?

2000 or 2001 on would have the check engine light from the loose gas cap. CHRYSLER Called it the LEAK DETECTION PUMP(LDP), and it was a PITA! It would often times throw a check engine light just for the heck of it, CHRYSLER programmed the wrong variables into it in it's first year, and it would set the light in under 20 seconds, well it takes upwards of 2 minutes to pull the tank down under a vacuum. I HATED the LDP with a passion, unfortunately though I was the only one in the shop that was able to efficiently use the LDP diagnostic machine:nut:.