Check engine light came on 2005 Hyundai Elantra and is orange. Autozone hoked it up to the electroinc diagnosis and said it shows code P0455. They said it is gas cap. Is this correct? We re-tightened gas cap and they said it should re-set the light after 50 miles of driving. If it does not then purchase a new gas cap. Does this sound correct?

We purchased a 2005 Elantra a year ago, 77000 miles. it has had a P0455 code, large evap leak, off and on since we got it. Can't find any large leak nor vacuum leak. Replaced purge valve. Removed and checked the charcoal canister; it appears to be okay. Blew out the lines; all are clear. Will have a smoke check in a couple days. Don't know what to expect. Am miffed with Hyundai for having such a finicky evap system. They seem to have been fiddling with it for years judging by the many slight variations found in the various models and years. They should design a robust, easily maintained system with codes that tell exactly where to look. PS, it ain't the gas cap. We've tried three of them. We purchased a 2005 Elantra a year ago, 77000 miles. it has had a P0455 code, large evap leak, off and on since we got it. Can't find any large leak nor vacuum leak. Replaced purge valve. Removed and checked the charcoal canister; it appears to be okay. Blew out the lines; all are clear. Will have a smoke check in a couple days. Don't know what to expect. Am miffed with Hyundai for having such a finicky evap system. They seem to have been fiddling with it for years judging by the many slight variations found in the various models and years. They should design a robust, easily maintained system with codes that tell exactly where to look. PS, it ain't the gas cap. We've tried three of them.