My 99 burb has a tendancy to throw a code sometimes. I can't exactly remember the code either p0442 or p0443 ( evap system small leak detected). the first time was several years ago and i unclipped the connections on the "evap canister" and cleaned the stems on the canister and made sure the fuel cap was tight. I cleared the code and that lasted several years. Now it is back after I had to replace the fuel cap because the cap failed Texas' emission test. Could this be caused by the crappy aftermarket fuel caps aquired at the local autoparts chain stores or is it in the evap lines either going to the intake manifold or the fuel tank. Where can one find the O rings located inside the clip on connectors if they are the culprit. I looked the lines over and none are apparent to have any wear spots or holes in the plastic portion of the hoses and the steel lines running under the truck are in their support clips and not appearing to be rubbing on anything to wear a hole in them. I could use some advice or guesses on the problem.

 

It could very well be a crappy cap, I have always heard that going with the OEM cap is the best bet....