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EVAP vent solenoid circuit error code P0446?

Tiny
DEQUESO
  • MEMBER
  • 2003 CHEVROLET ASTRO
  • 3.4L
  • V6
  • 4WD
  • AUTOMATIC
  • 81,000 MILES
New gas cap, checked purge valve, and checked good since cover was off but new in. Went 2 vent valve checked good could blow through checked wires 2 it good, checked vent valve elec it opened and closed. I clear the code it will come on after about 40 miles. It does not start hard it runs smooth no problem putting gas in idles good.
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Thursday, September 8th, 2022 AT 2:36 PM

16 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,380 POSTS
So, this code comes on when there is high resistance in the circuit, I would remove the connectors from the valve and the PCM to inspect the terminals for corrosion. Also here are the wiring diagrams for the EVAP system and a guide to help you do the tests.

https://www.2carpros.com/articles/how-to-check-wiring

Also, even though the valve tested good I would replace it anyway if you can't find a connection problem. Check out the images (below). Please let us know what you find. We are interested to see what it is.
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Friday, September 9th, 2022 AT 12:06 PM
Tiny
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Replaced the valve I clear the code 30 40 miles later comes back on. Now new gas cap new purge valve new canister vent valve still starts good runs good no bad idle no problem putting gas in clean underneath.
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Friday, October 14th, 2022 AT 9:55 AM
Tiny
KEN L
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Is it the same code P0446? If so it is high resistance in the EVAP wiring you will need to go over the wiring and follow the guide I gave in the first post.
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Saturday, October 15th, 2022 AT 12:05 PM
Tiny
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  • 38 POSTS
Yes, same code. It states evaporate emission system vent control circuit p0446? Can a mech with the right equipment trace the problem easier or is it trial and error. Also, what will it hurt because it will take me sometime 2 get 2 it because of my condition right now. I have a test light and ohms meter that's it?
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Saturday, October 15th, 2022 AT 1:47 PM
Tiny
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Oops, memory bad, I did check out both purge valve and canister valve had positive and negative reading 2 connectors that plugs into units, so I did have readings through the system?
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Saturday, October 15th, 2022 AT 2:34 PM
Tiny
KEN L
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If the wiring looks good, I would try another vent valve, it is common for these valves to go bad. Check out the images (below). Please let us know what you find.
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Sunday, October 16th, 2022 AT 2:06 PM
Tiny
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  • 38 POSTS
I replaced that vent valve so it is possible that it could be bad being new. When I replaced it, I zeroed out my odometer went 45 miles engine light came on? About same as old one?
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Sunday, October 16th, 2022 AT 4:45 PM
Tiny
KEN L
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Another thing you should check is the vacuum and vapor lines from the fuel tank to the engine, check for cracks or leaks.
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Monday, October 17th, 2022 AT 11:33 AM
Tiny
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  • 38 POSTS
Okay, back 2 Sq one. All lines look good from what I can see without being on hoist. So, purge valve and canister valve are good. I clear the code drive 20 miles come home 2 days later drive another 20 25 miles engine light comes on again it is a sealed unit so is the vacuum leak when it sits under pressure, been sitting 2 days took the gas cap off did not feel any pressure release don't know if this makes any sense?
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Tuesday, October 18th, 2022 AT 1:19 PM
Tiny
KEN L
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It sounds like the new gas cap is defective? The system must be air tight. The only other thing I can think of is if the canister is leaking, how did you check it?
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Wednesday, October 19th, 2022 AT 12:08 PM
Tiny
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I made sure there was power to the solenoid took the solenoid put 12 volt 2 it 2 make sure the piston opened and closed made sure I could blow through it when not activated. Is there any way I can check the gas cap. Like I said it sat 4 a couple of days took cap off could not feel any surge of pressure.
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Wednesday, October 19th, 2022 AT 2:50 PM
Tiny
KEN L
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You should not be able to blow through it when not activated.
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Thursday, October 20th, 2022 AT 11:21 AM
Tiny
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Getting valves mixed up I think the purge valve on the intake you cannot blow it is normally closed the canister valve by the gas tank is normally open until activated l believe I think?
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Thursday, October 20th, 2022 AT 1:40 PM
Tiny
KEN L
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Yep, that sounds right.
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Friday, October 21st, 2022 AT 11:20 AM
Tiny
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  • MEMBER
  • 38 POSTS
I think you may be on the right track about the gas cap. It is new but like u said it could be defective. It is from GM but a couple of things I tried points to it. I am going to order another one if it does not work, I am going to start from scratch after I order a vacuum pump so I can check everything. It will be a while before I will let you know what happens. Thank you for your help, made me understand the system, again thank you will be in touch.
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Friday, October 21st, 2022 AT 11:31 AM
Tiny
KEN L
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No problem, let me know what you find.
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Saturday, October 22nd, 2022 AT 12:50 PM

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