Does anyone know what the si diagnostics is for this code. po446. Is this top secret information that only the dealer has. Have already researched with no luck. How do you check to see which part you need. I will not go to the dealer. Already replaced gas cap per auto zone. Have taken vent valve off, cleaned and re assembled. Ckd hoses. Also checked charcoal canister for leaks. And valve on intake. How do you know whats wrong before buying wrong part. Maybe, I will just remove the light. Send me back to the 70's! Thanks for any help.

 

might need replace canister.

2003 Silverado Code Po446 - GM-Trucks.com

 

I would like a way to troubleshoot and deduct it down to right part instead of throwing money at the chevy dealer.

 

i had to replace that ventalation sensor next to the fuel pump when my truck threw a code similar to that (dont remember the code) and that fixed it. it's like 15 bucks and it's pretty easy to replace, un-bolt the canister disconnect 2 fuel lines and drop the tank a little and its right there.

 

P0446 - EVAP Vent System Performance. I suspect you have a bad vent solenoid assembly. The solenoid has two circuits. The Orn wire is power feed from the 4WS fuse in the underhood block. The Wht wire is the control. The PCM grounds the Wht wire. Backprobe the white wire and ground it. The vent solenoid should make an audible click when closing the valve. If it doesn't, change it. If the vent is working, inspect the canister for cracks. One other possibility is the fuel tank pressure sensor faulting, but you pretty much need a scan tool capable of reading it to verify. More than likely the vent solenoid is shot.