You do not get a P0455 code from a gas cap o-ring leak.

And you will likely get the code to come back up. Driving it 50 miles and/or starting it 4-5 times does not mean that 4-5 drive cycles were completed. There are specific requirements to the GM drive cycle.

 

...and here are the specifics.

 

You beat my edit! LOL

I did not remember to put the link that I had copied in when I hit submit.

 

No prob. Cover each other's back.