Advice Needed: MIL

I recently had the engine light come on in my 2001 Jeep Cherokee. I took it to the dealer and for $400+ they "fixed" my Leak Detection Pump, which was said to be defective. Now 2 weeks later, the light came on again and I was told that some type of filter canister (that holds charcoal??) is the problem. Can anybody help me understand what this system does and what could be wrong? Thanks

I think your dealership wrong mabe even guessing. Take your Jeep to your nearest Autozone and have them read the Trouble Codes. You may even be able to do this yourself by turning your key on-off on-off on-off and on. Count the Check engine light flashes and get back to me and I will try to tell you what is wrong. You may be able to repair yourself.

BTW what is your engine?

Thanks for the quick reply. Its a 4.0 liter 6 cyl.

See if you cand get the codes. But to directly answer your question above (I forgot) the canister is like a holding tank for your vaccum for the entire vaccum system.

I have the same vehicle with the MIL coming on also. Engine surges also. I tried the on-off-on-off-on-off-on but got no codes. No Autozone in my area. Any other methods to retrieve codes? Also to add to the charcoal canister question that gpowner had, it holds the fuel vapors in the fuel system temporary till engine cools.

Go to this website and it will tell you how to get your codes.
http://www.cybrrpartspro.com/chiltonautolibrary/root/

See if you cand get the codes. But to directly answer your question above (I forgot) the canister is like a holding tank for your vaccum for the entire vaccum system.

Actually, I believe the original poster above was talking about the Charcoal Canister (aka. Evaporative system canister). This is NOT a vacuum reservoir. Instead it is a charcoal filter that filters the gas vapors from the tank before they are inserted in the intake manifold.

-Nick