P0456 Check engine light

Hello forum members,

This is an awesome site and would really appreciate it if experts can guide me with my cars problem.

I have a 2002 hyundai sonata V6 with 65000 miles.

On thursday (7/19) the check engine light suddenly came on.
On saturday (7/21) took it to Autizone and the guy mentioned P0456 error code and reset it saying probably it must be the gas cap that was loose and tightened it.
Drove about 150 miles. Filled gas after that. Drove another 100 miles approx. and the check engine light came back on monday (7/22).
On monday (7/22) again went to autozone with the same P0456 error code. They reset it again.
This time the check engine light came back on after driving 70 miles.

The car is out of warranty. the hyundai dealers in boston just want to make money and say they do not accept outside codes and they will have to do run the diagnostics themselves and that costs $200 plus the $$$ to fix the problem.

I would really appreciate your opinion.

I am continuing to drive with the check engine light on and this time I shut the gas cap to exactly till I heard 3 clicks and have driven 40 miles and the check engine light is still on.

I really make sure the gas cap is tightly closed and there is no loss in gas mileage or driveablity of the car till now.

Will the car pass Massachusetts state inspection if I just keep driving it?

How can I go about identifying the problem as I know it could be so many things that could be wroing if its not the gas cap.... could be the hoses and seals in the vacuum line... Please advise on the best course of action for a student short on dough!!!!!!

With that code you could also have a vacume leak at the engine or your Purge vent solenoid could be defective..one other thing you might want to check out is your Evaporater canister to see if it has a cracked hose or maybe it has become disconnected!
 
                               WheelBrokerAng

Where is the purge vent solenoid?  My 2002 has the same condition.

A code P0456 is a very small leak in the evap system. 99% of the time replacing the canister close valve solves this concern. The valve is sticking open intermittantly it is very common with the Sonata and Elantra.