SOURCE: 2004 Pontiac Grand Prix Evaporative Canister
you should be able to fix it look for a can near the fuel tank that has vacuum hoses coming out of it and you should be able to just buy the bad solenoid
SOURCE: HAVE A TROUBLESHOOTING MESSAGE PO446
DTC P0446 Evaporative Emission (EVAP) Vent System Performance
The vehicle control module (VCM) monitors the performance of the evaporative
emission (EVAP) system by applying a predetermined level of vacuum to the
EVAP system and monitors the vacuum decay rate. The VCM sets this diagnostic
trouble code (DTC) if the vacuum decay rate is more than a predetermined
value. The VCM monitors the amount of vacuum and the amount of pressure
in the EVAP system by monitoring the fuel tank pressure sensor. For
this DTC, the VCM turns ON both the EVAP purge valve and the EVAP vent
valve when the Conditions for Running the DTC are met. This applies
an engine vacuum to a closed EVAP system. The VCM turns OFF both the
EVAP purge valve and the EVAP vent valve when the system reaches a correct
amount of vacuum. The EVAP system should quickly RELEASE the vacuum
in the EVAP system with the EVAP purge valve OFF and the EVAP vent valve
OFF (open). This test indicates a blocked or restricted EVAP vent path
if the EVAP system fails to release the vacuum quickly enough.
SOURCE: I have a 2004 Avalanche, 49K mileage, code PO446,
That is an EVAP code. its a vent control code. you can manually test it by powering it up if you know where its at. i cant remember exaclty where its at off the top of my head but its only 2 wires. using a volt meter you want to make sure power is getting to it, but you cannot activate it without dealer scan tool.hmmm if you can figure out which is ground and power when you give it 12 volts it should click. meaning your vent solenoid works and you have wiring problems or its leaking.
EVAP problems are hard to finde with out scanners. you can change the vent solenoid and hope it fixes it. but a code points you to the direction of a problem. hopefull its not wiring problems. in the northern states with snow. ice can pull out wires and also get clogged in the vent solenoid and lock it up. its either wiring or bad or a leaking solenoid. check condition of wires. if they look good try a vent soleniod.
if that doesnt fix it after a engine light reset and 2 weeks or so. then goto dealer. you need to reset it after repair. light will not go off on its own.GOOD LUCK
Michael
ASE certified.
plz rate
SOURCE: replacing the evap canister
It is the big black box on driver side front next to fender. It has to vacuum hoses going to it.
SOURCE: 2004 Chevy Cavalier 2.2 eco Automatic 94,000 miles
in my experience the usual culprit is the evap cannister. the problem is it gets moisture in it and freezes during winter thus cracking the plastic. if you lay under the car and look at the evap box it black plastic and if you see a loose or cracked hose or the box itself is cracked that is most likely it. as a side note you can check the gas cap and buy a new one to see if that rectifies the situation. lastly i don't think the gas tank should be suspect as you would probably notice if gas was leaking out of the tank. if you take the car to a dealer or shop they can do a smoke test and determine where the leak is.
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An EVAP canister, vent hose, or vent solenoid valve that has restricted flow may cause this DTC to set. Using a purge solenoid command with a scan tool will allow vacuum to be applied to the system instead of pressure. With the engine running, the EVAP canister vent solenoid valve open, and the EVAP canister purge solenoid valve commanded to 100 percent, the fuel tank vacuum should not increase to more than 5 inches H2O.
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An EVAP canister filter that is restricted can cause this DTC to set. Refer to Evaporative Emission Canister Replacement .
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Disconnecting one component at a time while the EVAP system is under flow will help to pinpoint a restriction in the system
Do you have a scan tool that reads data PID'S ?
Your FTP - fuel tank pressure sensor could be at fault !
If
The charcoal canisters also clog up. Do some diagnosing before you go changing parts.
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