Question

I have a Ford with engine code P0455, what is the meaning of the code?

Answer 1

This code is for a large leak in the evap system. This is usually caused by either a bad fuel cap, vent control valve or 

a sticking purge control solenoid. More often then not the vent control valve sticks open and allows for the large leak. 

You can remove the vent control valve, add power and ground and listen for it clicking. If you don't hear any noise it's 

no good and should be replaced.