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  #1  
Old 04-10-2012, 03:01 PM
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Default How to check a EVAP vent valve?

Hi friends.

One of my buddys got a problem with his 2005 Colorado.
Itīs a L5 3.5l engine.

I write this thread, because my buddy canīt speak english and german car shops donīt have any idea about Chevys.

The Colorado has the P0446 error. I know itīs something about the evap vent valve circuit.
I think the valve is dead, but before we pay the high shipping costs to germany, I want to check the Valve.

Can I apply a voltage at the pins to check that it works? I think, there are only two pins and if I apply a voltage it should close or open the Circuit, or am I wrong?

So, I hope the Valve is similar to a Blazer and you could help us.

Thanks a lot for your help, guys.

Best regards from germany.
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Last edited by christian1984; 04-10-2012 at 03:03 PM.
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Old 04-10-2012, 07:54 PM
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yeah you can jump the wire going to it and hear it click... usually on most vehicles they are really cheap so we usually just replace that at my work cause 95% of the time its the valve itself. you have to somewhere find the wiring diagram first and find which one to run a wire too. see if you can find a vent valve cheap, if so just replace it and see what happens first before you go jumping wires

sometimes if you get a vent valve leak it could be a line leak also. heck chevys are easier then german cars, we get volvos and vw's and every thing you can think of at my work. they are all different but very much the same.
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Old 04-19-2012, 03:05 PM
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Thank you for your answer abig84. I checked the valve next to the evap canister and it works. The failure stayed. So, Am I right, that there is a valve at the engine between the intake and the battery tray? And do anyone know how can I reach it? Thanks for your answers.
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Old 04-19-2012, 04:14 PM
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Quote:
Originally Posted by christian1984 View Post
Thank you for your answer abig84. I checked the valve next to the evap canister and it works. The failure stayed. So, Am I right, that there is a valve at the engine between the intake and the battery tray? And do anyone know how can I reach it? Thanks for your answers.
How did you test it? Clicking doesnt mean much in sol valves. And it needs to be exercised and tested for open flow {it closes when energized} several times.

The cause for a P0446 would probably be a clogged vent valve, or partially clogged or kinked line between it, canister, and tank pressure sensor.
Yes, I looked up the code then searched for details to make sure.
http://blazerforum.com/forum/diagnos...plained-35143/

The specific test looks to see how long the vacuum lasts once vent is opened
Quote:
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 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 tails to release the vacuum quickly enough.
Various other sites say the same
The valve in the engine area would be the purge valve. If it, or the line between it and canister failed -or the good old 'loose gas cap'- a different code would be set because it would have never gotten vacuum. Unless it somehow stuck open, constantly applying vacuum.

Whenever you open the filler cap to add fuel and pressure is released, there's a hint right there!
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Last edited by pettyfog; 04-19-2012 at 04:22 PM.
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Old 04-19-2012, 11:56 PM
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Thanks for your answer. I checked the valve by applying a voltage. Hear it clicking and blowed some air through it. We checked the lines and don't seen any cuts. But we didn't seen all of the lines. When we add fuel we didn't hear a sound of vacuum or something like that. Because I didn't understand everything, maybe my questions could be a little bit stupid
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Old 04-27-2012, 03:08 PM
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Damn, today my buddys Colorado ran into reduced power mode and then it won't run anymore. So it's towed by roadside assistance to his dealer. I hope he finds the failure and it costs not so much.
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Old 05-30-2012, 10:32 AM
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After many days of waiting, the failures were found.

The P0446 was caused by a defective tank pressure sensor and the reduced power was caused by a broken pcm...

So, it costs almost 1000$...

Thanks from my buddy for your fast answers and your help.

I think, this thread could be closed. ;-)
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Old 05-30-2012, 10:32 AM
 
 
 
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