I have a 2003 silverado 1500 4.3L it's throwing codes P0442,P0446,P0455,P0496 I have changed the charcoal canister vent valve, purge valve, gas cap reset the codes and they haven't gone away any ideas on what It could be or what i can do will be greatly appreciated

 

just for giggles i would test your purge valve with a vacuum pump. i got two of them once, once from AC the other was a cheaper version. the ac brand one wouldnt hold vacuum but the cheaper one did. ive heard of people buying 4 and 3 out of the 4 being bad

 

I will give it a try tomorrow it's a dorman brand I was only getting p0442 before i replaced the purge valve and ever since i ended up with that plus p0446, p0455,p0496

 

i think dorman brand was the one that worked for me.