I have two codes coming up on my PCM. P0449 and P0455. Respectively these are Evaporative Emission Vent Solenoid Control Circuit Evaporative Emission (EVAP) System So does anyone know what may be going on with the truck and what I need todo the correct/fix it? At least where to start? At the advice of the parts guy, he said that changing the gas cap might help. Did that nothing changed, one point for the parts guy for selling something. :grrrrrr: Truck is a '03 ext cab 1500 with a 5.3 & 4x4.