Location of evap canister vent valve

there are like 1billion cars noW doing this.

1. the gas cap was loose or bad !!!
2. theN the driver did not know it takes 30 driving cycles to clear the CEL lamp. OOPS 30? OBD2 DOES THAT. PER SERVICE MANUAL RULES, IF YOU READ THEM.
3. the fuse did not blow, or you'd have not asked where it is, I get that.!

99% of the time the cap was just loose or bad
my car the 1% time, the purge solenoid stuck
and my walmart silicon spray'd there (INSIDE IT) ended FAILURE for 50,000 more miles.
learn to buy AND USE a scan tool (borrow, rent ,buy)
tighten the cap again
scan the pCM see the cel lamp reasons./
push reset on the toll (CEL goes off if lucky and not 100 other DTC errors set)
and drive 3 times or more and the CEL stays off.

the other resets are(NO SCAN TOOL,. REALLY?)
1: PULL BATTERY LUG FOR 15MIN AND PUT BACK
OOPS RADIO GOES DEAD. dang
2: PULL ALL IOD FUSES. THE PCM MEMORY FUSE ONLY.
Ecm F29 IS IT(MEM) (PCM) 10AMPS
ALL DTCS NOW GONE, STORED. THE DATA FELL; INTO THE BIT BUCKET AS THEY SAY

IF ALL TESTS AND WILD GUESSING REPLACING ALL EVAP; VALVES. THEN COMES THE SMOKE MACHINE TESTS.
TO FIND THE LEAK
THIS IS AND EPA MANDATED MONITOR IN USA.
FOR SURE. THE 2 FUSES FOR BOTH EVAP VALVES ARE HERE.

DTC P0449: Evaporative Emission (EVAP) Vent Solenoid Control Circuit

Circuit/System Description
An ignition voltage is supplied directly to the evaporative emission (EVAP) canister purge solenoid valve. The engine control module (ECM) grounds the EVAP canister purge solenoid valve control circuit through an internal switch called a driver. The ECM monitors the status of the driver. The EVAP canister purge solenoid valve is pulse width modulated (PWM). A scan tool will display the amount of ON time as a percentage.
Battery voltage is supplied to the EVAP canister solenoid valve. The ECM grounds the EVAP canister vent solenoid valve control circuit through an internal switch called a driver. The ECM monitors the status of the driver. A scan tool will display the commanded state of the EVAP canister vent solenoid valve as ON or OFF.

P0449
Ignition ON, engine OFF, command the EVAP vent solenoid ON and OFF with a scan tool.
Listen for a click when the valve operates. Verify that both the ON, and the OFF states are commanded.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing
Ignition OFF, disconnect the harness connector at the EVAP canister purge or vent solenoid valve.
Ignition ON, verify that a test lamp illuminates between the voltage supply circuit terminal A and ground.
? If the test lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and the voltage supply circuit fuse is open, test or replace the EVAP canister purge solenoid.
Connect a test lamp between the voltage supply circuit terminal A and the control circuit terminal B.
Command the EVAP canister purge solenoid valve to 50 percent with a scan tool, or the EVAP canister vent solenoid valve ON and OFF. The test lamp should respond to the command.
? If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
? If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
If all circuits test normal, replace the appropriate solenoid valve.

This is how to test electrical circuit for the vent solenoid .

Found this on YouTube. How to Test and Replace EVAP Pressure Sensor P0450 Its behind the drivers side rear tire.

It's located under the vehicle back behind the fuel tank , Installed in the canister ! Remove the EVAP canister vent solenoid valve from the canister !
Rotate the EVAP canister vent solenoid valve counterclockwise in order to release it from the locked position.
Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle . Disconnect the evaporative emission (EVAP) canister harness electrical connector (2) from the EVAP vent solenoid valve. Clean away any debris that may be present around the EVAP canister vent solenoid valve.
Remove the EVAP canister bolt. Lower the EVAP canister.

your vehicle has a vent valve solenoid located on the evap canister under the back end of the vehicle. You most likely have a bad vaccuum line going to the evap caniser. Have the vehicle smoke tested to verify. If no leaks are found replace the vent valve solenoid

P1446 - EVAP Canister Vent Control Valve Close
EVAP canister vent control valve remains closed under specified driving conditions.

This solenoid valve responds to signals from the ECM. When the ECM sends an ON signal, the coil in the solenoid valve is energized. A plunger will then move to seal the canister vent. The ability to seal the vent is necessary for the on board diagnosis of other evaporative emission control system components.

This solenoid valve is used only for diagnosis, and usually remains opened. When the vent is closed, under normal purge conditions, the evaporative emission control system is depressurized and allows EVAP Control System (Small Leak) diagnosis.

The EVAP canister vent control valve is located on the EVAP canister and is used to seal the canister vent.

Symptoms:
- Engine Light ON (or Service Engine Soon Warning Light)

About the possible causes that your must solved:
- EVAP control system pressure sensor and the circuit
- Blocked rubber tube to EVAP canister vent control valve
- EVAP canister vent control valve
- Water separator
- EVAP canister is saturated with water


Hope this helps.

Hi, your EVAP vent valve is likely stuck closed. The valve is under the car near the fuel tank. Remove the valve and check to see if it's stuck. You may be able to restore operation by cleaning the valve with carb cleaner. The valve should be open when no voltage is applied. I have pasted instructions below from autozone.com. Please let me know if you have any questions, and thanks for using FixYa.
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.

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.

Continuous Memory Diagnostic Trouble Code (DTC) P0442 indicates that a fuel vapor leak has been detected [as small as 0.10 cm (0.04 inch)] in the Evaporative Emission (EVAP) system.
Note: Prior to performing the following diagnosis inspect the Canister Vent Solenoid (CV) for contamination. A situation may exist where contamination holds open the Canister Vent (CV) solenoid enough to set DTC P0442 and also plugs the port to atmosphere enough to keep system from being vented quickly.

• After market parts and accessories nonconforming to the EVAP system specifications.
• Damaged, cross threaded or loosely installed fuel filler cap.
• Small holes or cuts in fuel vapor hoses/tubes (EVAP canister tube, EVAP canister outlet tube or EVAP return tube) in the EVAP system.
• Loose fuel vapor hose/tube connections to EVAP system components.
• EVAP system component [EVAP canister purge valve, fuel tank pressure (FTP) sensor, canister vent (CV) solenoid, fuel vapor control valve tube assembly or fuel vapor vent valve assembly] seals leaking.
• CV solenoid partially open when commanded closed.
• EVAP canister leaking.
• Check for presence of fuel filler cap.
• Verify that the CV solenoid is properly seated on the EVAP canister (if possible).
• Visually inspect for cut or loose connections to fuel vapor hoses/tubes in following locations:
  • EVAP canister to EVAP canister purge valve.
  • EVAP canister to fuel vapor vent valve assembly.
  • fuel vapor control valve tube assembly to fuel tank (if applicable).