The code is for a large evap leak.
The car has a self check system were it tests how well sealed the gas tank and evaporation tubing from the canister to the engine is sealed.

Most often it is a failed gas cap seal but it could also be quite a few other things.
After refuelling is the car hard to start for a few seconds?
Have any evap parts been changed recently?

 

A common cause can be failure of the 'close valve' mounted on the charcoal canister to seal off the evap system during the test cycle. That could be the failure of the valve itself, or a major leak in the rubber tubing anywhere from purge valve to the gas tank, to the close valve, or to the fuel filler area, or even the gas cap itself. Also exists the possibility of an dirty or failed electrical connection to the close valve.
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This shop doesn't have a smoke machine? How did they check for a leak? What process? There's not a whole lot to an evap system, Sounds like they don't have a big idea on how to diag. May want to get your money back.

 

Thanks for the replies so far. Yes the first thing I had done was a smoke test, no sign of a leak I watched and walked around with them as it was done. I had already changed the PCV valve and the tubing. And replaced the gas cap "just in case". I have had it in 3 different shops (not the dealership though) I have had every sensor checked in the engine compartment the charcoal canister. As I stated I ran out of money to continue diagnosing the mystery leak. The shop said it would be another 2.5 hours to pull the fuel tank off and check there. So I am stumped and wonder if anyone else had these problems or if the code I provided meant something to someone, I apparently don't speak Hyundai ODB.

 

Rich to Lean sensor switch time(calculated)

To me that can be one or two O2 sensors (pre-cat) getting too slow to react. It doesn't trigger yet a failed O2 sensor code.

 

The p0455 code, as indicated in a post by another member, points directly to a large air leak in the EVAP system, and only finding and fixing its cause will solve you inspection test.

In an earlier post, I gave the following link to material available from Hyundia that explains the EVAP system tests that the computer performs and assign error codes, such as the leak codes for small and large leaks.

http://www.hyundai-forums.com/194-y...-1989-2005-sonata/161850-just-comment-evap-system-not-question.html#post1288128

Reading this material may help you understand the system and guide your followup.

As just a comment, I proffer that most large leaks will occur in or near the charcoal canister area. I would be surprised if the vacuum leak is in the gas tank, as the tank vents thru rubber tubing to the charcoal canister then thru the close valve to atmosphere. On that age car, the rubber tubes connected to the charcoal canister could be rotting and leaking, the aged hose clips could be rusted and not sealing properly. And as I mentioned previously if the close valve is not operating correctly due to electrical fault or actual failure, you have a large "leak" on your hands.

I highly suggest you at least drop the canister from its mounting tray and carefully inspect all the tubing connections at the cannister and at the other end where they connect to hard tubing leading to the gas tank , the filler vent, and to the purge valve tube leading to the engine compartment. Probably you will find your problem within a couple of feet of the cannister. Those are all short lengths of tubing, and at their age it might be wise to just replace the tubing and the clips to be sure several small leaks do not add up to a big leak.

Good luck.

It is extremely unlikely you actually have a leak in the gas tank or canister walls themselves.