The other day my check engine light came on and I read the code and it said something about the gas cap but the car doesn't have on. Can anyone give me dome advice?

 

What do you mean it doesn't have a gas cap? lol P0457 refers to a leak in the EVAP. Its basically telling you that when it performed the leak test on the evap/fuel tank system it found a large leak, meaning it could not pull vacuum on the system. Most likely cause is a loose or missing gas cap. Maybe a broken vacuum line as well.

 

he may have the capless fuel filler setup. the only way to accurately diagnose an evap concern is to use a smoke machine and scantoool. anything else is just guessing.

 

My 12 V6 doesn't have the gas cap either..don't know if I like that or not Have their been any known problems with the capless system?

 

sometimes the capless filler doesnt seal due to dirt, i have also seen some fail, not just on mustangs, but on any car that uses this setup. not real common, but it happens.

 

Once I cleared the code it hasn't come back. My inspection is due this month I just hope it doesn't come back when I go to get it