The car has now been in the shop 3 times for the same "Check Engine" light indication.. The first time was at 20,000 miles.. the dealer I took it to said the code indicated a loose gas cap.. I questioned that, but made an effort to put it on tight.. then at 52,000 miles, it came on again.. I did the 4 key (on/off) sequence and the light would extinguish for about a week then come back on.. then several days later off... then on again and off again...This week at 54,000 miles I took it to the dealer again, and he said it was a faulty gas cap, and replaced it..All should be fine now I was told.. he very next day the light came on again... and is still on.. but I am sure it will reset after several starts.. I guess it is back to the dealer again who is 50 miles away.. any idea what is going on before I make the return trip?

I'd be curious to know what code you are getting, but it sounds like some kind of "evap leak" code. Try replacing the canister close valve, that's a very common thing besides the gas cap with an evap leak code.

What is the "4 key (on/off) sequence "? I had the same for months. The little filter forward of the charcoal filter was replaced and the light never came back again. In the vent system, there is small filters (blue & white), make sure they are clean. The mechanic at the dealer told me that if the charcoal filter is heavier then a certain value, it must be replaced and if it should be replaced, it is costly. Start with the small one ($10.00). Should fix the light.

The 4th return trip to the dealer today revealed a code indicating a faulty oxygen sensor.. You guessed it, "Not in stock".. but will be here Monday.. which equates to yet another trip back to the dealer to get it put in... The Check engine light that now comes on, only stays on for 2 or 3 engine starts then clears... Maybe it was coincidence that the gas cap (air leak) and the sensor went bad at the same time, but makes me wonder???

Filling the gas with the car running will set the 'gas cap' code too (IIRC P0440), otherwise, yeah, could be anything in the evap system. Wont hurt anything but be hella expensive. If its under warranty, get it done before it runs out.