2003 GMC Sierra engine light

455 is gross leak in the evap system, you have to locate the canister, and check all hoses, and look for cracks and or disconnected hose. also check the solenoid.

is there any best method for checking hoses ect other than visual as some are up on top of gas tank. To check the valve is it or would it be the purge valve or a vent valve??? I know canister is under by gas tank and vent valve is up on top front side of gas tank. Should it all just be taken out and inspected/replaced

I'm one to try to take a short cut, when working on vehicles, which I believe is a bad habit. but in this case, that is the only way we can see what is above the fuel tank. so we may have to pull it, I would of course leave it for last..this vehicle is not that old to be having worn pieces. I would start with the purge valve , you should check the vent too. these have diaprams in them, and that is what goes bad. so check both valves. and keep me posted please,

would you know where i could find a schematic showing the hose routing for emmision controls. I been looking all over truck and everything looks fine yet could be missing some. There is no sticker in engine compartment and my haynes serviced manual does not have one. Is this available on internet ????

Hey thanks again

yeah you can probably find it on the internet. but I am gonna use my references and see if I can come up with something. also what size is your truck 1500,2500?

well I cannot find a diagram, but it looks like everything is pointing to the purge and vent solenoids, they both will need to be checked, I suspected, with a truck not even seven years old yet that the hoses would be compromised, do you know where the two solenoids are? the vent solenoid is on the left side of the gas tank and the purge solenoid is on the engine, and I sent to your email a diagram of the purge solenoid