I did a little bit of work on the Escape (2001 V6) the other day, changed out the fluids and all of that stuff, and replaced the gasket that goes from the MAF to the IAC, since it was ripped.

It's running a lot better, and not annoying of a hiss (Unless the air is on) but the engine light kicked back on today while driving back from work, so I stopped at Autozone and pulled the codes.

P0455
P1504

I haven't seen any leaks, or anything that would cause this since I changed out that gasket and cleaned up the valve a bit. I haven't had a total loss of gas mileage, getting about 275 with 14 Gallons give or take depending if I do some city driving.

Thanks!

 

Found this thru internet: OBD-II Trouble Code: P0455 Evaporative Emission Control System Leak Detected (no purge flow or large leak)

Code P1504: Intake Air Control circuit malfunction
Code P0455: Evaporative Emission Control System Leak Detected (no purge flow or large leak)

Check the above website for causes related to Code P0455