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: Looking for the evap canister vent valve on a 2006 Silverado
if you look underneath the vehicle on drivers side in the area beneath drivers you with see a plastic rectangular sort of shaped box this is evap canister and vent valve is there in this area.
SOURCE: 2006 Chev Silverado 2500HD
your evap vent filter is plugged. you can find it in front of the gas tank underneath. blow it out and it will be fine.
SOURCE: have a 2004 Avalanche, Problem
it sounds like you may have a fuel tank vent valve staying closed causing pressure in the tank when filling up.
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