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: 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: What does failed canister vent solenoid mean on my
it a sealed system that take gas fumes and bruns them threw the engine to lower emmision into the air.there a valve in the system as like the canister is anonther part that filters,but anyway the vent valve vents preasure or vapors if its no working system cant seal or vent when it needs to,hope this helps.
SOURCE: where is the canister vent solenoid located on a
right on the top of the canister it's even part of the canister and can't be removed you just change the canister
SOURCE: 2006 gmc sierra 1500 4.3 . check engine light on.
More than likely the evaporator vent valve.
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