Check Engine Light - 4.0 TJ

JeepMonkey · #1 (**permalink**) 07-25-2007, 09:01 PM

Has anyone put a header on a 4.0 and had the CE light come on? At first I thought it was an exhaust leak, but I fixed that and the light is still on. Could it be the difference in temperature is causing it? I'm sure the header runs cooler now. I have to have it smogged next month and I'm pretty sure it is an automatic "no-pass" if the light is on.

Bounty__Hunter · #2 (**permalink**) 07-26-2007, 01:45 AM

What year jeep? Could be you just need a scantool hooked up to reset the light.

JeepMonkey · #3 (**permalink**) 07-26-2007, 01:13 PM

That's what I was thinking. It's an '01. I assumed it would turn off when the problem was corrected, but I could be wrong.

LauraBoston · #4 (**permalink**) 07-26-2007, 07:26 PM

I will eventually turn off if the problem is corrected, BUT it's takes sometimes quitle a while. If you cycle your key it will give you the code. Is your odometer digital? it will give it there, if it's not I think the CEL will blink and you gotta count them...

JeepMonkey · #5 (**permalink**) 07-27-2007, 02:06 AM

Quote:

Originally Posted by LauraBoston

I will eventually turn off if the problem is corrected, BUT it's takes sometimes quitle a while. If you cycle your key it will give you the code. Is your odometer digital? it will give it there, if it's not I think the CEL will blink and you gotta count them...

Learn something new everyday! I did that and it actually gave me the code P0455 (A large leak has been detected in the evaporative system). Now I need to figure out exactly what that is.

Is it the canisters right below the exhaust header? It also said it could be caused by a bad gas cap. My buddy has a scanner and he said he should be able to reset the light since I think I've fixed the leak. If it isn't fixed then the light should come back on and I'll start over.

Thanks again for the help!

redrooster · #6 (**permalink**) 07-27-2007, 09:46 AM

Monkey,
Did you hook the O2 back up?

JeepMonkey · #7 (**permalink**) 07-27-2007, 10:04 AM

02 (All 4) were hooked back up.

Just for grins & giggles I unplugged the battery this morning for 5 mins before I left for work. When I hooked it up and left the light never came back on. Hopefully this does the trick. I didn't think the battery trick would work since it doesn't make sense that Joe Driver should be able to turn the light off for smog requirements. I'm not complaining though!

Bounty__Hunter · #8 (**permalink**) 07-27-2007, 01:24 PM

Sounds like a loose or bad gas cap. Could be that simple.

LauraBoston · #9 (**permalink**) 07-28-2007, 03:30 PM

Could be a gas cap, could be split hoses. Look at all the hoses, from purge solenoid to canister, and the ones from the NVLD pump or whatever EVAP system you have, there is a pump under the hood, and a green cap that looks like a tire valve stem in it, those hoses crack all the time. Sometimes, if you're daring you can test your gas cap by, brace yourself, you kinda gutta get a good seal around it with your lips and blow...stay with me here, if it's the gas cap you'll be able to blow into it. If your caps good, no air will leave your mouth. You follow?

I'm willing to bet split hoses. I'v been know to be wrong, before.

I just read up more...did you find the problem?

LauraBoston · #10 (**permalink**) 07-28-2007, 03:33 PM

oh and with the battery thing...when one disconnects the battery it clears PCM short term memory where codes are stored on some makes and models (mostley olderish), probably was a loose cap...if you got gas in the past few days.

JeepMonkey · #11 (**permalink**) 07-28-2007, 08:18 PM

I've been driving it for two days and the light hasn't come back on. I'll be sure to get a new gas cap before I smog it. Every car I've smogged for the last 10 years has had to have a new gas cap every time. I think it's a scam between the cap company and the govn't to get more money. Thanks for all the advice!

TwistedCopper · #12 (**permalink**) 07-28-2007, 09:00 PM

Quote:

Originally Posted by Bounty__Hunter

Sounds like a loose or bad gas cap. Could be that simple.

That would be my first guess. I hate to say it but it's worth the extra $$$ to get one from a dealer. The cheapie Stant ones failed me twice by triggering that idiot light within 3 months of buying them (on my '00 XJ). I broke down and bought one from Jeep and it lasted the whole last year I owned it.