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P0446 code


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#1 acevetss

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Posted 06 December 2006 - 10:34 PM

I've read the other posts about this topic as well as my manual but I'm only getting more confused as to where to start. The manual says it's "vent system performance" and that the system will throw a code if a leak is detected. Then later it says the canister or hoses are the most likely cause. But the posts say it's a blockage, which I would lean towards because I was driving dirt roads one weekend about 2 hours prior to the SES light coming on. (But I also overfilled the tank, which I normally do so I don't think that would have caused it.) I've checked the lines and connections I can see, but without pulling the tank I can't check them completely. I was going to replace the vent purge solenoid but the posts say it's the vent hose assembly (another says vent valve solenoid-is that the same thing?). Some posts are for GMC and some for newer years than mine so I'm not sure which part numbers apply-2000 Tahoe 2wd 5.3 69k. Will replacing the vent valve solenoid most likely solve my problem? If dust has caused it, has it gotten in the canister too or is it just blocking the vent valve solenoid?

#2 GM-Tech

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Posted 07 December 2006 - 12:47 AM

Here's the "official" word on the subject. I'm sure this will take care of it for you.


Subject: LR4, LM4, LM7, L59, LQ9, LQ4, L18 DTC P0446 (Restricted/Blocked EVAP Vent Path) Set, Service Engine Soon (SES) Lamp Illuminated (Replace Vent Solenoid and Bracket) #04-06-04-055A - (03/20/2006)



Models: 2000-2003 Cadillac Escalade

2002-2003 Cadillac Escalade EXT

2003 Cadillac Escalade ESV

2000-2003 Chevrolet Suburban, Tahoe

2002-2003 Chevrolet Avalanche

2000- 2003 GMC Yukon, Yukon XL

with 4.8L, 5.3L, 6.0L, 8.1L Vortec™ V8 Engine (VINs V, P, T, Z, N, U, G -- RPOs LR4, LM4, LM7, L59, LQ9, LQ4, L18)


--------------------------------------------------------------------------------

This bulletin is being revised to add updated warranty information and enhance the content. Please discard Corporate Bulletin Number 04-06-04-055 (Section 06 -- Engine/Propulsion System).


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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 solenoid, resulting in restricted air flow, may cause this condition.

Correction
DO THIS
Replace the EVAP vent solenoid with a more robust vent solenoid.

DON'T DO THIS
DO NOT Replace the EVAP canister or other EVAP parts.


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 solenoid and bracket. This new vent solenoid 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 and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
Remove the bolt retaining the vent valve bracket.
Disconnect the electrical connector.
Disconnect the canister vent valve hose.
Install the new vent valve bracket, P/N 15105605, to the vehicle with the retaining bolt.
Tighten
Tighten the bracket mounting bolt to 12 N·m (106 lb in).

Install the new vent valve, P/N 10382105, to the bracket.
Reinstall the electrical connector.
Reinstall the canister vent valve hose.
Lower the vehicle.
Clear the DTC.
Parts Information
Part Number
Description
Qty

15105605
Bracket, EVAP Emission Canister Purge
1

10382105
Valve, EVAP Emission Canister Control
1


Warranty Information
For vehicles repaired under warranty, use:

Labor Operation
Description
Labor Time

J6441
Valve, Evaporative Emission Canister Vent Solenoid and Bracket - Replace
Use Published Labor Operation Time




GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION


© Copyright General Motors Corporation. All Rights Reserved.

#3 acevetss

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Posted 07 December 2006 - 09:37 AM

Thanks for the info and fast reply!

#4 acevetss

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Posted 11 December 2006 - 06:29 PM

Replaced the vent valve solenoid but the P0446 code is still coming up. If it's not dust related what else would cause this code?

#5 GM-Tech

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Posted 11 December 2006 - 08:20 PM

Replaced the vent valve solenoid but the P0446 code is still coming up. 


Oh man, I was sure the valve would have fixed it. Does this mean you cleared the code and it came back? The P0446 and light is not going to go away just because you replaced the valve. So, have you cleared it?

There are probably a couple dozen things that could cause your problem. If the code was cleared and came back, you need to do a little in-depth diagnosis to figure out what's going on. This would require equipment you don't have so I don't know what to tell you to do next.

#6 acevetss

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Posted 11 December 2006 - 10:21 PM

yes I cleared the code, replaced the valve, and it came back.

#7 Norseman

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Posted 12 December 2006 - 09:51 AM

yes I cleared the code, replaced the valve, and it came back.

<{POST_SNAPBACK}>


I had the same issue. Turned out to be the purge solenoid on top of the intake manifold. I've seen a mechanic bud of mine squirt a little sea foam in the valve to free carbon that gums it up. He said it works about half the time. The other half just end up needing a new purge solenoid. Give it a try, worse case you buy a new solenoid the one you have isn't working anyway. :cool:
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#8 GM-Tech

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Posted 12 December 2006 - 03:23 PM

Yep, could be the purge valve too, though I haven't seen any failures in those as compared to the vent valve. Still, there's always a possibility.

The problem here is, without doing a thorough and complete diagnosis, throwing parts at it can get awful expensive very fast. That's the problem with guessing.

#9 Burbman

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Posted 12 December 2006 - 05:39 PM

If the code was cleared and came back, you need to do a little in-depth diagnosis to figure out what's going on. This would require equipment you don't have so I don't know what to tell you to do next.


Sounds like it's time for a trip to the local dealer.....
2001 Suburban K2500LT
8.1L Big Block and 4.10 rear
American Racing AR-23 16x8 rims
Bridgestone Dueller AT Revo LT265/76-16-E tires
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#10 acevetss

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Posted 16 December 2006 - 05:03 PM

It was the evaportive canister. I guess the dust and gas from overfilling turned to mud and clogged it up. Hopefully the new filter design keeps that from happening again. I guess the GM CAD program doesn't factor in real world conditions.

#11 tnsherrie

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Posted 02 March 2010 - 02:37 AM

Hi,
I have a 1999 Yukon Denali 5.7L that is throwing the P0446 code and SES light is on. I have looked everywhere under the truck and cannot find the evap canister, vent solenoid or anything that resembles them. Does anyone have an idea of where these parts would be on my truck so I can check and see if the are blocked?

Thanks in advance!

#12 Head3Hunter

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Posted 11 March 2010 - 10:53 AM

Check the frame cross member in front of the rear axle. The control valve is located there on the back side. The canister is located under the drivers seat on the Outside of the Vehicle.

Hi,
I have a 1999 Yukon Denali 5.7L that is throwing the P0446 code and SES light is on. I have looked everywhere under the truck and cannot find the evap canister, vent solenoid or anything that resembles them. Does anyone have an idea of where these parts would be on my truck so I can check and see if the are blocked?

Thanks in advance!



#13 99silv53

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Posted 13 March 2010 - 10:06 AM

Ok seems like im the odd ball out here, I have a 1999 Silverado 5.3l, What does this canister look like? is it the square plastice box mounted in front of the gas tank?

#14 murray79

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Posted 17 March 2011 - 10:38 PM

It was the evaportive canister. I guess the dust and gas from overfilling turned to mud and clogged it up. Hopefully the new filter design keeps that from happening again. I guess the GM CAD program doesn't factor in real world conditions.


Is the evaportive canister alot of money? I replaced my vent valve solenoid and purge valve still have po446. Should i try evap canister? P.s this just happen after changing the fuel pump a week ago

Edited by murray79, 17 March 2011 - 10:40 PM.


#15 hoochi

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Posted 28 March 2011 - 05:28 PM

It was the evaportive canister. I guess the dust and gas from overfilling turned to mud and clogged it up. Hopefully the new filter design keeps that from happening again. I guess the GM CAD program doesn't factor in real world conditions.


Is the evaportive canister alot of money? I replaced my vent valve solenoid and purge valve still have po446. Should i try evap canister? P.s this just happen after changing the fuel pump a week ago


I have been getting the same code I replaced my fuel pump a few months ago.




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