Hello I had my car since Oct 2014 and only put 10k miles on it because I take the bas to work. But just today I got a check engine light come on reading P0456 according to my OBD II it says Generic-powertrain - Evaporative emission system leak detected ( very small leak ) should I be concern and bring it to the stealership? I can't even reset the code when I remove the negative for 20mins it still stays on.

 

Your owners manual should tell what to do if the car tells you to check your gas cap. For the moment, treat this code as the same thing.

Can you erase the code with your code reader?

Make sure the gas cap is fully tightened and the leash isn't caught in the threads.
Stop by an Autozone (or similar parts store) and have them erase the code, if you cannot.
If the code resets again within a couple drives then you probably do have a problem that needs looked at.

 

My gas cap came loose once and the car actually displayed a message to "check the gas cap". So maybe this is different?

 

If the system detects a very large leak it assumes the gas cap was left off or very loose and displays the message.

OP has a code for a very small leak (pinhole size) which CAN be caused by a cap not fully tightened. Or a damaged seal, or similar.
That's certainly not the only possible cause but sure is worth checking the cap and resetting the computer memory to see if it happens again right away.

 

Don't know where you live, but has it rained a lot there lately? My '09 Fit gave the same error after an unusually rainy spell. Not sure why, but after resetting the gas cap it went away.

 

It can be other than the gas cap. The cap is most common and not tight enough is the most common reason. Make sure when tightening the cap to turn it more than one click, 4-5 should suffice. If that's the cause the code should clear after a few days or drive cycles.

 

Thank you and everyone else for the information and suggestions. When I first read the code and the description I thought a hose or connection had came loose since I saw my mpg drop before my eyes on a short trip from home to work 10 miles. I never knew that it could be the gas cap as I got a different message before to check the gas cap. This actually scared the crap out of me because I was on the freeway and this day I took my 2 year old to work and didn't want to get stuck on the freeway with her. Its strange that the engine light came after using half the tank of gas and this car only have under 10k miles. I tighten the gas cap 5 clicks and reset the code and it hasn't come back since 20 miles of driven. I don't drive this car much but if it comes back I'll report it here.

thank you
Johnny