2002 chevy 1500 v-6 p0449 code will not remove

SOURCE: 2005 chevy 1500 silverado eng.

P0449 is the evap vent valve solenoid circuit malfuntion.
P0455 is an evap gross leak
Perhaps the gross leak code has to do with the vent valve. Find the vent valve. It should be near a rectangle evap canister. Maybe under the bed. The small vent line from the fuel tank will go to it. The solenoid is near the cansiter. With the key off the valve will be open. With the key on it should be closed. You may try disconnection the hose and blow through it with both key off and on and see if air will pass through. If the valve has died and is stuck open, that can be the huge leak.

If it is not the leak then a smoke machine should be used. Easier than searching the lines for bad o-rings, splits, or whatevers.

SOURCE: 2006 Chevy silverado 1500 I changed evap sensor

replace evap.. canester ...full of fuel from someone toping off tank

SOURCE: error code p0449

i have code reader says p0449 is evaporative emission control system - vent valve / solenoid circuit

SOURCE: We hooked up an OBD11 Auto Scanner to our 2005

P0449 has to do with the Evap System. The problem could be with wiring short circuit, Could be the EVAP canister purge valve or the ECM.
P0455 has to do with the evap system as well. Could be a leak in one of the hoses to the evap system so you need to check all lines to the evap system. There is also one hose that connects to the top of the tank that we have seen come loose. Could also be a intake leak or a problem with the Canister purge valve. You can fix these yourself somewhat. I would trace down all the lines first to see if anything has come loose under the vehicle to the Black plastic EVAP canisters. Without being able to check the valves you will probably have to take it to a shop to have them checked out or pay the price to replace the valves and gamble they are the problem.

SOURCE: Getting codes P0455 and P0449. From what I read,

The vent solenoid valve has been redesigned to correct the problem you are having. I would recommend purchasing the dealer component.
I am not aware of any aftermarket parts suppliers.