2001 Tahoe Evap Emissions Question - Any GM Techs? - Chevelle Tech
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  #1  
Old Aug 5th, 07, 11:01 AM
TW TW is offline
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Default 2001 Tahoe Evap Emissions Question - Any GM Techs?

My 2001 Tahoe "Check Engine Soon" light is on and the code reader says it is the Evaporative Emissions System. I replaced the gas cap, but it didn't help. From what I have heard/read the system is fairly simple, consisting of a vent valve, a pressure sensor and hoses.

Can anyone tell me the procedure to test the individual components of the system. The manuals I have do not go into the detail needed to troubleshoot to the component level.

The light has been on for about 2 weeks now and is really annoying. The last time it came on it went off on it's own right before I needed to get it safety/emission inspected. If it matters, it has 140k miles on it and runs perfect.

Any help here would be appreciated!
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  #2  
Old Aug 5th, 07, 11:18 AM
SSuper Dave SSuper Dave is offline
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Default Re: 2001 Tahoe Evap Emissions Question - Any GM Techs?

We had a machine at our dealership that pumped smoke thru the evap fitting under the hood. You then use a light to find the leak. They are ususally very small and you might not see it otherwise Follow the lines and it you don't see the problem, you may have to take it to the dealer, at least for diagnosis.
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  #3  
Old Aug 5th, 07, 12:33 PM
jeffss454 jeffss454 is offline
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Default Re: 2001 Tahoe Evap Emissions Question - Any GM Techs?

Document ID# 1539908
2001 Chevrolet/Geo Tahoe - 4WD


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

DTC P0446 (Restricted/Blocked EVAP Vent Path) Set, Service Engine Soon (SES) Lamp Illuminated (Replace Vent Solenoid and Bracket) #04-06-04-055 - (Jul 28, 2004)
DTC P0446 (Restricted/Blocked EVAP Vent Path) Set, Service Engine Soon (SES) Lamp Illuminated (Replace Vent Solenoid and Bracket)
2000-2003 Cadillac, Chevrolet and GMC Full-Size Utility Models

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
DON'T DO THIS

Replace the EVAP vent solenoid with a more robust vent solenoid.
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 SI Document ID #737171.
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 Nm (106 lb in).

Install the new vent valve, P/N 15750484, 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
1

15750484
Valve, EVAP Solenoid
1


Parts are currently available from GMSPO.

Warranty Information
For vehicles repaired under warranty, use:

Labor Operation
Description
Labor Time

L0260
Valve, EVAP vent solenoid and bracket - Replace
0.3 hr




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.


--------------------------------------------------------------------------------
Document ID# 1539908
2001 Chevrolet/Geo Tahoe - 4WD
this is what was wrong with mine,do you have a way to get it scanned and get a code?
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  #4  
Old Aug 5th, 07, 8:29 PM
TW TW is offline
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Default Re: 2001 Tahoe Evap Emissions Question - Any GM Techs?

Thanks Guys. I'll check the hoses, etc for leaks first. Do the GM techs test the vent solenoid before replacing or is it just cheaper to replace it?

Thanks Again,
Tom
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  #5  
Old Aug 5th, 07, 11:24 PM
Dave Birdwell Dave Birdwell is offline
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Default Re: 2001 Tahoe Evap Emissions Question - Any GM Techs?

IIRC, they're pretty cheap. I just bought one for my T-Blazer, it was about $30.
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  #6  
Old Aug 6th, 07, 12:11 PM
TW TW is offline
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Default Re: 2001 Tahoe Evap Emissions Question - Any GM Techs?

Dave, if that's what it costs, I'll just replace it after checking the hoses, etc.

Thanks for the info!

Tom
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  #7  
Old Aug 6th, 07, 5:13 PM
70malibumikey 70malibumikey is offline
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Default Re: 2001 Tahoe Evap Emissions Question - Any GM Techs?

to test these we hook up the smoke machine to the vehicle, then we go in with the tech 2 and command the vent valve closed, after the valve has been closed, and you can ussually verify it closing by listening for an audible click, turn on the smoke machine, the system is now closed & full of smoke, now with a high power light watch the hoses for some, you mainly look @ the vent valve since the are so common, then after you replace it test again. If the valve doest click when commanded on you check with a dvom to see if the vent is being comanded @ the valve, if no power, trace that problem, it it is powered replace the valve
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  #8  
Old Aug 6th, 07, 7:41 PM
TW TW is offline
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Default Re: 2001 Tahoe Evap Emissions Question - Any GM Techs?

Thanks 70Malibumkey, I'll check this thing out this weekend.

Thanks again,
Tom
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  #9  
Old Aug 7th, 07, 9:16 PM
ironhead ironhead is offline
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Default Re: 2001 Tahoe Evap Emissions Question - Any GM Techs?

Also..be aware of the fact that a skewed fuel tank pressure sensor can lead you on a wild goose chase.If the vent valve seals and passes the flow and smoke test and the purge solenoid introduces vacuum when commanded on at 10% intervals..the ftp sensor should react accordingly and also show the dump when purge is disabled and the vent valve opens.The fow test can hang a vent valve.The positive pressure will hold a healthy vent valve closed after command is removed.remove the gas cap and shoot a little shop air down the neck to unseat the rollover ball and watch the ftp return to zero.
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Old Aug 8th, 07, 1:20 AM
Chris R Chris R is offline
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Default Re: 2001 Tahoe Evap Emissions Question - Any GM Techs?

Do you remember what the actual number for the trouble code was?
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  #11  
Old Aug 8th, 07, 10:57 PM
TW TW is offline
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Default Re: 2001 Tahoe Evap Emissions Question - Any GM Techs?

Ironhead, Thanks for the great info!

Chris, I had someone read the code for me and they only told me that it was the evap system. They didn't give me the number. But, I just got my own reader in the mail today, so I will post the code number tomorrow.

Thanks for the reply's!

Tom
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  #12  
Old Aug 9th, 07, 12:28 PM
TW TW is offline
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Default Re: 2001 Tahoe Evap Emissions Question - Any GM Techs?

The code reader is showing code P0446, which looks like it translates to a Purge Valve Short. Is the Purge valve likely bad, or is that unlikely and it's probably wiring or something?
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