The check engine light has been triggered on my 01 Cherokee. My first guess was my gas cap... which I clicked down a few extra ticks... a half tank later, it was still on. I filled the tank, and the gas over-filled (the pump didn't auto-stop at full). about 60-70 miles later, the light is still on. I took it to my mechanic, who said that the codes were coming back for the gas cap.
Any ideas what the h3ll I'm doing wrong?

 

could be a bad gas cap, or something else in the gas tank like seals.

 

x2. probably need a new cap. I've had a few go bad on me with other vehicles.

 

did you clear the code? or did you just tighten the gas cap?

 

They cleared it when I took it in.
Thanks for the info. I didn't know a cap could go bad, so to speak.
I'll give it a try.
trdb

 

It must say small evap leak for a code,If the new gas cap doesn't fix it then its most likely a hose on the canistor.Put a new cap on it,then you will have to wait for it to cycle thru it's check list, might take a couple of days after you reset the cel.

 

from what ive seen a gas cap usually results in a large leak code.. its silly, but put a 5$ cap on it and see if it helps.

 

on my 01 xj, i can turn it till it clicks 50 times and it doesn' get any tighter, CEL would come on for that, so i found that if i turn it the required # of clicks, and then a little more (between clicks) it tightens it down just enough that it won't throw the code.

 

Are you one of these know it alls or what,I was giving an opinion to the OP not you.Do you own a real code reader ( not the ones from auto zone) Well I got one and have read what I wrote . So please keep your opinion to the OP and not me. Thank you.Your agruement doesn't try and solve the OP's problem.

 

I got the CEL and an 0955 code, massive leak code and sure enough, the new gas cap replacement didn't fix it.

The evaporative cannister underneath the vehicle in front of the drivers side rear wheel has little elbow hoses that crack and leak over time and are known to cause this CEL as well.

A quick way to check for leaks is to spray soapy water on the gas cap and hoses which run all up to front of the vehicle. It will form bubbles if any air is leaking out.

The DTC data is stored in the computer and the type of reader, as long as it's making a connection according to the OBDII communication protocol shouldn't really matter. It either reads the data stored and provided by the computer or it does not.

 

The canister your looking for is out back by the gas tank , the front one is for vacuem for the heater control doors.

 

I'm going to regret doing this.....but he did in fact say, in front of the driver's side REAR wheel. Which is just about correct, though on my 2000 XJ, it's more toward the middle of the vehicle. But he wasn't pointing to the vacuum one up front.

 

Whatever.
Once your under the vehicle there's only one of em !!