Question about Chevrolet Tahoe

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Codes came up

The eigin light came on the diagnosis code comes back as po446

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  • roe cooper Apr 23, 2009

    how much it cost to fix

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  • Chevrolet Master
  • 3,854 Answers

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
Bad PCM

Good luck and hope this helps

Posted on Apr 20, 2009

  • Harvey N Tawatao
    Harvey N Tawatao Apr 23, 2009

    Sorry it's hard to say how much it would cost to fix, It could be as easy fix as a crack vacum tube, Replaceing the gas cap for around $10.00 to the other things i mentioned before.


    If there was dirt in the vent valve that's not in there any more it could just be as easy as to re-setting the ECM to clear the codes.


    They this for now, turn the ignition key to the run position with out the engine running. Remove the fuse to the ECM for about 5 sec, then place it back in. Start the truck and it may stall oon you but let it, just start it up again. The ECM is just learing the engine again like the day it came off the assembly line and all the codes should be cleared. 


    If the service light come's back then your P0446 is still there and your going to have to use a TECH2 to pin point which part of the EVAP system failed and needs to be changed. 


    Good luck and hope this helps.

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Code po446 what is it


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This happens when the engine speed is at a higher RPM level and is supposed to send the vapor to the engine to be burned instead of VOC'S going into the atmosphere .But its a crazy lie the last time I filled up more VOCS got into the atmosphere then a gas tank vent could do in 6 month or so .
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