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Go Back   Hummer Forums by Elcova > Hummer H2 Discussion Forums > Technical Discussion and Customizing your H2

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  #1  
Old 06-18-2009, 07:20 PM
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Default Eng. Fault code PO446 Evap. System need Help.

I would appreciate any help I could get with this.
I have had an engine warning light for a while now with several codes and have replace several components.

I am down to one code left.
PO 446 the scanner says evap system control fault.

What is this and can anyone explain what needs to be done to correct it?
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  #2  
Old 06-18-2009, 08:05 PM
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Default Re: Eng. Fault code PO446 Evap. System need Help.

It sets due to a restriction in the evap system, could be a pinched hose, evap cannister, evap vent solenoid, fuel tank pressure sensor. In most cases i have found the vent valve is plugged or not working, it is located behind the cannister approx right below the driver side b pillar on the outside of the frame. If you disconnect the line that goes to the evap cannister from the vent valve and find lots of dust inside you will need to replace both the cannister and vent valve as well as clean any dust out of the line
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  #3  
Old 06-18-2009, 08:17 PM
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Default Re: Eng. Fault code PO446 Evap. System need Help.

Quote:
Originally Posted by BKLYNH2
I would appreciate any help I could get with this.
I have had an engine warning light for a while now with several codes and have replace several components.

I am down to one code left.
PO 446 the scanner says evap system control fault.

What is this and can anyone explain what needs to be done to correct it?

Make sure your gas cap is screwed on tight. This is most likely the cause of the code. Evap is not likely an issue in this vehicle unless you had a supercharger or evap port clog. Did you get gas and overflow the tank? Also a possibility. In any case evap can only be tested from an OBD scanner and pass when it is COLD.
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  #4  
Old 06-18-2009, 08:20 PM
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Default Re: Eng. Fault code PO446 Evap. System need Help.

A loose gas cap will set a p0455, evap system large leak detected
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  #5  
Old 06-18-2009, 08:24 PM
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Default Re: Eng. Fault code PO446 Evap. System need Help.

I would look at the gas cap first . than if after you replace the gas cap and drive it for 3 or 4 drive cycles if the MIL light won't go out check all evap hose's and the canister .
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  #6  
Old 06-19-2009, 06:37 AM
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Default Re: Eng. Fault code PO446 Evap. System need Help.

See above, P0455 is a code that will set with a loose cap, P0446 is an evap restriction. Not trying to be a prick, but each code has its own diagnosis and i do work on these on a daily basis.
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  #7  
Old 06-19-2009, 06:42 AM
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Default Re: Eng. Fault code PO446 Evap. System need Help.

DTC P0446

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 inches H2O in a calibrated time, this DTC sets.
The following table illustrates the relationship between the ON and OFF states, and the Open or Closed states of the EVAP canister purge and vent solenoid valves.
?
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  #8  
Old 06-19-2009, 06:33 PM
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Red face Re: Eng. Fault code PO446 Evap. System need Help.

yes I know a PO446 is a evap code haveig to do with the canister path being blocked or restricted ,and a purge selenoid valve is often time the culprit or a bad hose or pinched or blocked hose ,all I saw was your post with a PO445 my bad .
Quote:
Originally Posted by HUMTECH
A loose gas cap will set a p0455, evap system large leak detected
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Last edited by IRA51 : 06-19-2009 at 06:54 PM.
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  #9  
Old 06-19-2009, 11:36 PM
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Default Re: Eng. Fault code PO446 Evap. System need Help.

I have one thing to add. I live in Michigan and its very "moist" here. the same code had appeared on mine 3 times in 5 years. I just cleared it and it stayed gone for a long time. it seemed to set if we had a huge change in temp or humidity. being as the tech guy is in AZ. and the Problem is NY. I believe that is lost in translation. I tend to wonder if the NY guy is fighting the moisture issue I was having. seemed to set if I had less then 1/2 tank when the temp changed.
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  #10  
Old 06-20-2009, 03:21 AM
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Default Re: Eng. Fault code PO446 Evap. System need Help.

Quote:
Originally Posted by BKLYNH2
I would appreciate any help I could get with this.
I have had an engine warning light for a while now with several codes and have replace several components.

I am down to one code left.
PO 446 the scanner says evap system control fault.

What is this and can anyone explain what needs to be done to correct it?
I had the cannister full of mud and water once. I'm sure you're is toast.
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  #11  
Old 06-21-2009, 12:36 AM
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Default Re: Eng. Fault code PO446 Evap. System need Help.

Thanks for all the replies guys. I should have a better idea after this weekend is over. Interestingly both ideas have credibility. I once had a very catastrophic fuel overspill but I also reinstalled the original gas cap shortly thereafter which since I hadn't been using it for 3 years was in new condition. I think that Humtech is probably right on and Rox's comments really help confirm that. I have beat the crap outta my truck over the years and driven through a lot of junk, mud and water. The effects of this are appearing everywhere these days. I will have a look at the evap canister and components tis weekend and maybe someone can tell me which parts need to be replaced when I report back.
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Old 06-24-2010, 06:31 PM
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Default Re: Eng. Fault code PO446 Evap. System need Help.

I know this is a old thread but what was the outcome? I have been fighting a p0446 code for months. I have replaced the soleniod on the intake, cleaned the prefilter, checked all the lines, and replaced the gas cap. I still have the light.
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  #13  
Old 11-19-2011, 04:19 AM
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Default Re: Eng. Fault code PO446 Evap. System need Help.

this thing happend on one of my h2's today. I had the tank almost empty.
On my way to the gas station to fill up the tank, it cleared, but I don't know if it will come back...
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