I have been dealing with the P0446 code for months. It is for Evaporative Emission System Vent Control Circuit. I have replaced the Vapor Canister Vent Solenoid Valve 25932571 twice (I also checked the wiring on the plug and didn't see any problems), the Evaporator Emission Canister Purge Solenoid Valve 12581282 twice, and the Vapor Canister 22963841. Each part I used genuine GM and not Chinese knock offs. I clear the code and it will come back after a couple days. What are the next steps? I have not tried replacing my gas cap but when I inspect it, it looks fine as does the rubber O ring on it. Sometimes when I pump gas it will cut off, but it will eventually fill up without issues after I readjust it a few times. There is also a fuel tank sensor I read about to possibly replace but that seemed to be for a different code. Is my next step to blow out the evap lines? If I need to blow out the evap lines with compressed air can someone please explain it as if I were a 5 year old? I don't want to screw anything up. What line do you put the air through and which lines need to be disconnected? Does the fuel tank need to be dropped to blow the lines out? Any help is greatly appreciated!

 

 

Cause:

• The fuel tank vacuum is greater than -12 inches H2O vacuum for 5 seconds.
• OR
• The fuel tank pressure (FTP) is less than -2.5 inches H2O or more than +5 inches for 60 seconds after a cold start.

 

Good Stuff Z man.

I had a code with the fuel system years ago. Can't remember what the Code # was. But the dealer replaced the Purge valve on top the the fuel tank and the intake manifold suck in purge valve on the intake. Seems they both fire off at the same time..I think BWTFDIK, Anyway.. I use to top off my fuel tank at gas up time.

My Mechanic at the dealer (at that time was a HUMMER dealer) Scolded me for topping off the tank and told me the excess overfill farks up that purge valve on the tank top. Since then ...as soon as the pump nozzle clicks off.. I'm Done filling.

I was a Bad boy.

 

maybe that if it's not the solenoids.

 

Very good thread. I'm having the a similar issue with my 09 HUMMER H2, but its the evaporative system, slow leak code that I have.

 

Just don't over fill it... When It clicks off your done. My 09 has been a good boy ever since I started clicking off.

 

UPDATE: So I went to replace the fuel tank pressure sensor, as it was basically the only thing left I hadn't replaced for P0446. My fuel pump was so insanely rusted that when I tried to take the sensor out, it snapped in half leaving the rubber grommet part inside the pump. There is barely enough room to fit your hand in there after taking off the wheel well liner and fender flare. There was no option left but to replace the entire pump, which made sense anyway as it includes the sensor and my pump was rusted to hell. The check engine light is now gone. Posting this update to help others chasing down this annoying evap code.

 

 

Yes it is Dreaded ...Had one years ago with the 2009 H2.. In one of my posts explained that the dealer mechanic used a closet door mirror with magnets that he stuck to the floor and put his drop light up in the area and worked in reverse while looking in the mirror while the 2 was on the lift. Next time get you a cheapy Walmart closet mirror and some magnets on each corner and glue them on and stick the mirror to the floor and rock on.....L.O.L.