Question about Chevrolet Tahoe
The eigin light came on the diagnosis code comes back as po446
P0446 This indicates that a part of the EVAP control system is no longer fuctioning correctly. EVAP emission canister purge is contolled by a valve which allows engine vacuum to pull stored fuel vapors from fuel tank into the engine to be burned, rather than be vented to atmosphere.
A vacuum switch is used to detect when flow exists. If the PCM commands purge and sees that the switch is closed (indicating no detected purge flow) P0446 is set.
When the vapor pressure rises to a specified point, the ECM opens the VSV for canister closed valve. Pressure will increase rapidly because of the air allowed into the system. No increase or an increase below specified rate of pressure increase indicates a restriction on the air inlet side. The ECM closes the VSV for pressure switching valve.
This action blocks air entering the fuel tank side of system. The pressure rise on the fuel tank side is no longer as great. If there was no change in pressure, the ECM will conclude the VSV for pressure switching valve did not close.
It is probly your evap canister vent valve is restricted. GM has a new design assy that repositions the vent so dirt wont plug it up, i suggest taking to a dealer to make sure, thay can use a tech2 to acurately diagnose the concern.
Good news is Likely, no symptoms will be discernible to the driver, other than the illuminated Check Engine Light.
Bed news A code P0446 could mean one or more of the following has happened:
Bad vacuum switch
Broken or damaged EVAP line or canister
Open in PCM purge command circuit
Open or short in Voltage feed circuit to Purge Solenoid
Faulty purge solenoid
Restriction in EVAP solenoid, line or canister
Corrosion or resistance in purge connector
Good luck and hope this helps
Posted on Apr 20, 2009
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Posted on Jan 02, 2017
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