I have a 2007 Chevy Silverado K1500. I have the EVAP Vent Valve Malfunction issue. I have replaced the vent valve and hoses, and the gas cap. The purge valve passes the bench test. Code will reset but comes back after about 20 miles of driving. Is there a relay that runs this system or is it computer controlled? What other ideas are there to permanently rid this issue. Thanks in advance for any help you can give.

code is a malfunction with the EVAP system. check the things below. bad gas cap, leaking fuel tank, charcoal canister is broken, faulty vent control valve, bad canister purge valve or loose or broken hose (EVAP) Good luck Mike L.

This code has nothing to do with a gas cap . P0498 Evaporative Emission System Vent Valve Control Circuit Low

DTC P0446: Evaporative Emissions (EVAP) Vent System Performance
Circuit/System Description
This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path. The control module commands the EVAP canister purge solenoid valve Open and the EVAP canister vent solenoid valve Closed. This allows vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the EVAP canister purge solenoid valve Closed and the EVAP canister vent solenoid valve Open. The control module monitors the fuel tank pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 inch H2O in a calibrated time, this DTC sets.
Diagnostic Aids
?€¢
An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP canister vent solenoid valve inlet, or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill problem.

?€¢
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.

?€¢
An EVAP canister filter that is restricted can cause this DTC to set. Refer to Evaporative Emission Canister Replacement .

?€¢
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 !

Ignition ON and fuel cap removed, verify that the FTP sensor parameter is between 1.3-1.7 volts. ?‡'
If not within the specified range, go to the FTP sensor section in Circuit/System Testing.

1. Install the fuel cap.
2. 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 12 inches H2O.

?‡'
If the fuel tank vacuum is greater than the specified range, go to the restriction section in Circuit/System Testing.

If

have you check the purge valve, and your vacuum lines? here's a vid you might want to check out:

https://www.youtube.com/watch?v=AlfOSMmisPg

code p1446 refers to evaporative emission (EVAP) canister purge valve---vent control valve malfunction===causes--wiring--EVAP pressure sensor---hose leak/blockage---EVAP vent valve---EVAP canister contaminated ---ECM

PO449-- Evap Vent Valve/Solenoid Circuit Malfunction

PO441--Evap Purge Valve Incorrect Flow
PO 443,444,445 Purge Control Valve Issues


There was no reason to change the gas cap or
purge control valve

Didn't Google the code & use it correctly to diagnose
the problem

most fuel systems are not vented if cap has vent that could be your prob or you have a prob with your evap system front or rear sencer could be bad or your evap canister could have mosture in it you need to have a systems check to find out what code has been thrown weather it's electrical or emmissions

Some might have an ses p0446, evap emissions vent circuit low. If you take it to the dealer they want 300-400.00 to fix the problem. GM has a service bulletin on this condition and have the updated part for 180.00, thats suppose to eliminate this issue.

Basically the problem is, the evap purge vent valve gets clogged with dirt, especially if the truck is used in dirty conditions. Well I figured there had to be a cheaper way to cure this problem.

Here it is:
1) find the location of the vent valve; its under the truck, locate the charcoal canister on the front of the gas tank and trace the vent line to the vent valve.
2) Take the bracket loose with a 5/8 wrench.
3) Spin the valve around so the side with the hole is facing you.
4) Take an air compressor and blow the vent valve out.
5) reinstall and clear the code and it's fixed.

Now I know the updated part from gm is supposed to keep the valve from clogging ever again, but why spend the money when all you have to do is blow out the vent valve every 50k-100kmi and save your $$$!

Subject: DTC P0446 (Restricted/Blocked EVAP Vent Path) Set, Service Engine Soon (SES) Lamp Illuminated (Replace Hose/Evaporative Emission (EVAP) Canister Vent Asm) #02-06-04-037A - (02/02/2005)
Models:
- 1999-2003 Chevrolet Silverado Models
- 1999-2003 GMC Sierra Models
--------------------------------------------------------------------------------
This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 02-06-04-037 (Section 06 -- Engine/Propulsion System).
--------------------------------------------------------------------------------
Condition
Some customers whose vehicles are operated in dusty type environments, such as farming or mining off-road type applications, may comment about the illumination of the instrument panel SES light, with a DTC of P0446 (Restricted/Blocked EVAP Vent Path) being set.

Cause
Dirt and dust intrusion into the EVAP canister vent hose assembly, resulting in restricted air flow, may cause this condition.

Part Number 15086429 Hose Asm-Evap Emis Cnstr Vent


Removal & Installation
Purge Solenoid Valve-2.2L (L61) Engine

1. Disconnect the evaporative emission (EVAP) canister purge valve harness connector.
2. Disconnect the vacuum pipe from the EVAP canister purge valve.
3. Disconnect the purge pipe from the EVAP canister purge valve.
4. Remove the EVAP canister purge valve and bracket.
5. Remove the EVAP canister purge valve from the purge bracket.
6. Inspect for carbon release in the EVAP canister purge valve ports.
   

To install:

1. Install the EVAP canister purge valve on to the purge bracket.
2. Install the EVAP canister purge valve and bracket. Tighten the purge bracket nut to 71 inch lbs. (8 Nm).
3. Connect the purge pipe to the EVAP canister purge valve.
4. Connect the vacuum pipe to the EVAP canister purge valve.
5. Connect the EVAP canister purge valve harness connector.
6. Remove the air cleaner outlet resonator.
7. Disconnect the EVAP canister purge valve harness connector.
8. Disconnect the engine purge pipe from the EVAP canister purge valve.
9. Disconnect the engine vacuum pipe from the EVAP canister purge valve.
10. Remove the EVAP canister purge valve mounting bracket attaching bolt.
11. Remove the EVAP canister purge valve along with the mounting bracket.
12. Installation is the reverse of the removal procedure. Tighten the bracket bolts to 71 inch lbs. (8 Nm).

Purge Solenoid Valve-2.4L Engines

1. Remove the front purge pipe from the evaporative emission (EVAP) canister purge valve.
2. Remove the rear purge pipe from the EVAP canister purge valve.
   NOTE The EVAP canister may have released carbon particles, which caused this part to fail, and may cause damage to other components. Check the EVAP canister for loose carbon before returning the vehicle to service.
   
3. Disconnect the EVAP canister purge valve electrical connector.
4. Insert a screwdriver between the EVAP canister purge valve and the mounting bracket in order to release the lock tab.
5. Remove the EVAP canister purge valve mounting bracket attaching nut, if replacing the bracket.
6. Remove the bracket.
   

To install:

1. Install the mounting bracket and the attaching nut for the EVAP canister purge valve. Tighten the nut to 71 inch lbs. (8 Nm).
2. Slide the EVAP canister purge valve onto the mounting bracket. Make sure the lock tab locks the valve in place.
3. Connect the EVAP canister purge valve electrical connector.
4. Connect the rear purge pipe to the EVAP canister purge valve.
5. Connect the front purge pipe to the EVAP canister purge valve.

Vent Solenoid Valve-2.2L & 2.4L Engines

1. Raise the vehicle
2. Loosen the EVAP canister vent valve hose clamp and slide the clamp down the hose away from the EVAP vent valve hose connection.
3. Remove the hose from the EVAP canister vent valve.
4. Remove the EVAP canister vent valve by placing a pry bar between the valve and mounting surface, and moving the valve forward.
5. Remove the clip from the EVAP canister vent valve harness connector
6. Disconnect the EVAP canister vent valve harness connector.
   

To install:

1. Connect the EVAP canister vent valve harness connector
2. Install the clip into the EVAP canister vent valve harness connector.
3. Install the EVAP canister vent valve by pushing the mounts into the original holes.
4. Lubricate the hose end with lubricant.
5. Install the hose to the EVAP canister vent valve.
6. Slide the EVAP canister vent valve hose clamp down on to the hose connection at the EVAP canister vent valve.
7. Lower the vehicle.

Hope this help (remember commetn and rated this).

P0446 = Evaporative Emission Control / System Vent Control Circuit Malfunction.

Check it, and before you replace the Evap Canister read this:

Subject: DTC P0446 (Restricted/Blocked EVAP Vent Path) Set, Service Engine Soon (SES) Lamp Illuminated (Replace Hose/Evaporative Emission (EVAP) Canister Vent Asm) #02-06-04-037A - (02/02/2005)
Models: 1999-2003 Chevrolet Silverado Models
1999-2003 GMC Sierra Models
--------------------------------------------------------------------------------
This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 02-06-04-037 (Section 06 -- Engine/Propulsion System).
--------------------------------------------------------------------------------
Condition
Some customers whose vehicles are operated in dusty type environments, such as farming or mining off-road type applications, may comment about the illumination of the instrument panel SES light, with a DTC of P0446 (Restricted/Blocked EVAP Vent Path) being set.

Cause
Dirt and dust intrusion into the EVAP canister vent hose assembly, resulting in restricted air flow, may cause this condition.

Correction
After following the Service Manual diagnostic P0446 and determining that the EVAP canister vent valve is the cause of the SES light, replace the existing EVAP canister vent hose assembly with a new assembly, P/N 15086429. This new assembly has an enhanced filtering capability and a filter element that can be easily removed and cleaned. To ensure correct installation, follow the procedure below.

Raise the vehicle. Suitably support the vehicle.
Disconnect the EVAP canister vent valve electrical connector.
Disconnect the vent valve pipe at the EVAP canister.
Remove and retain the EVAP canister vent valve bracket mounting bolt.
Disengage, from the underbody, the two vent valve pipe clips securing the pipe to the underbody.
Remove and discard the complete EVAP canister vent hose assembly.
Position and secure the new assembly to the underbody using the existing hole and mounting bolt.
Tighten
Tighten the bracket mounting bolt to 12 N·m (106 lb in).

Install the two vent valve pipe clips into the existing underbody holes.
Connect the vent valve pipe to the EVAP canister.
Connect the EVAP canister vent valve electrical connector.
Lower the vehicle.
When properly installed, the new EVAP canister vent hose assembly will be positioned outboard of the original installation location. This new location provides clearance for accessing the filter element for cleaning purposes. To access the filter element, disengage the filter cover to valve locking finger by gently lifting the finger upward while simultaneously rotating the filter body clockwise. After approximately 45 degrees of rotation, the filter can be disengaged from the valve by gently pulling outward. The filter cover can then be removed and the filter element and body can be washed with soap and water. Prior to reinstalling, ensure that the body and filter element are dry.

Parts Information
Part Number 15086429 Hose Asm-Evap Emis Cnstr Vent

Hope help with this.

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.