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  #1  
Old 01-21-2011, 08:09 PM
00Sierra 00Sierra is offline
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Question service engine light code PO449

My service engine light came on a couple of days ago on my 07 Yukon 4wd. The code is PO449. I cleared the code and tightened my gas cap as was recommended and the service engine light (and same code) came back on in a few miles. I am just looking for anyone who might can tell me what is going on. Thanks to all who respond!
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Old 01-21-2011, 09:59 PM
Molson02536 Molson02536 is offline
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Quote:
Originally Posted by 00Sierra View Post
My service engine light came on a couple of days ago on my 07 Yukon 4wd. The code is PO449. I cleared the code and tightened my gas cap as was recommended and the service engine light (and same code) came back on in a few miles. I am just looking for anyone who might can tell me what is going on. Thanks to all who respond!
Code P0449 indicates that there is a problem with your Evaporative Vent Valve Solenoid. On your truck it is on the right hand side of the fuel tank.

A fuel cap alone will NOT repair this code. I would get a new fuel cap as well, though because I find that the GM Fuel Caps go in about 2-3 years. I used to do Emissions work in Mass at a speed shop.

Go to a GM dealership and ask for the Evaporative Vent Valve Solenoid Assembly and a Fuel Cap for your Yukon and replace the parts mentioned above. Only use factory OEM parts for this repair, aftermarket parts will only last a few weeks and your doing the job allover again.

Good luck and keep us posted.
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Old 01-21-2011, 10:27 PM
00Sierra 00Sierra is offline
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Is this solenoid located in the fuel tank or to the right of the fuel tank? I'm all for replacing this solenoid and fuel cap with OEM parts. The auto parts store I went to to read this code told me to go to a mechanic for this problem as they had no parts to offer me. I appreciate you giving me this information. on a scale of 1 to 10 how difficult do you think replacing this solenoid is? Thanks again!
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Old 01-22-2011, 06:34 AM
Molson02536 Molson02536 is offline
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Originally Posted by 00Sierra View Post
Is this solenoid located in the fuel tank or to the right of the fuel tank? I'm all for replacing this solenoid and fuel cap with OEM parts. The auto parts store I went to to read this code told me to go to a mechanic for this problem as they had no parts to offer me. I appreciate you giving me this information. on a scale of 1 to 10 how difficult do you think replacing this solenoid is? Thanks again!
EVAP 101:

The evaporative emission (EVAP) control system limits fuel vapors from escaping into the atmosphere. Fuel tank vapors are allowed to move from the fuel tank, due to pressure in the tank, through the vapor pipe, into the EVAP canister. Carbon in the canister absorbs and stores the fuel vapors. Excess pressure is vented through the vent line and EVAP vent solenoid valve to the atmosphere. The EVAP canister stores the fuel vapors until the engine is able to use them. At an appropriate time, the control module will command the EVAP purge solenoid valve ON, allowing engine vacuum to be applied to the EVAP canister. With the EVAP vent solenoid valve OFF, fresh air is drawn through the vent solenoid valve and the vent line to the EVAP canister. Fresh air is drawn through the canister, pulling fuel vapors from the carbon. The air/fuel vapor mixture continues through the EVAP purge pipe and EVAP purge solenoid valve into the intake manifold to be consumed during normal combustion. The control module uses several tests to determine if the EVAP system is leaking.

Large Leak Test
This tests for large leaks and restrictions to the purge path in the evaporative emission (EVAP) system. When the enabling criteria has been met, the control module commands the EVAP vent solenoid valve ON and the EVAP purge solenoid valve ON, allowing vacuum into the EVAP system. The control module monitors the fuel tank pressure (FTP) sensor voltage to verify that the system is able to reach a predetermined level of vacuum within a set amount of time.

Small Leak Test
The engine off natural vacuum (EONV) diagnostic is the small-leak detection diagnostic for the evaporative emission (EVAP) system. While previous leak detection methods were performed with the engine running, the EONV diagnostic monitors the EVAP system pressure or vacuum with the ignition OFF. Because of this, it may be normal for the control module to remain active for up to 40 minutes after the ignition is turned OFF. This is important to remember when performing a parasitic draw test on vehicles equipped with EONV.

The EONV utilizes the temperature changes in the fuel tank immediately following a drive cycle to use the naturally occurring vacuum or pressure in the fuel tank. When the vehicle is driven, the temperature rises in the tank. After the vehicle is parked, the temperature in the tank continues to rise for a period of time, then starts to drop. The EONV diagnostic relies on this temperature change and the corresponding pressure change in a sealed system, to determine if an EVAP system leak is present.
The EONV diagnostic is designed to detect leaks as small as 0.51 mm (0.020 in). The diagnostic can determine if a small leak is present based on vacuum or pressure readings in the EVAP system. When the system is sealed, a finite amount of pressure or vacuum will be observed. When a 0.51 mm (0.020 in) leak is present, often little or no pressure or vacuum is observed. If the test reports a failing value, DTC P0442 will set.

Canister Vent Restriction Test
If the evaporative emission (EVAP) vent system is restricted, fuel vapors will not be properly purged from the EVAP canister. The control module tests this by commanding the EVAP purge solenoid valve ON, commanding the EVAP vent solenoid valve OFF, and monitoring the fuel tank pressure (FTP) sensor for an increase in vacuum. If the vacuum increases more than a calibrated value, DTC P0446 will set.

Purge Solenoid Valve Leak Test
If the evaporative emission (EVAP) purge solenoid valve does not seal properly fuel vapors could enter the engine at an undesired time, causing driveability concerns. The control module tests for this by commanding the EVAP purge solenoid valve OFF and the vent solenoid valve ON, sealing the system, and monitors the fuel tank pressure (FTP) for an increase in vacuum. If the control module detects that the EVAP system vacuum increases above a calibrated value, DTC P0496 will set.

Check Gas Cap Message
The control module sends a class 2 message to the driver information center (DIC) illuminating the Check Gas Cap message when a malfunction in the evaporative emission (EVAP) system and a large leak test fails.

EVAP System Components
The evaporative emission (EVAP) system consists of the following components:

EVAP Canister
The canister is filled with carbon pellets used to absorb and store fuel vapors. Fuel vapor is stored in the canister until the control module determines that the vapor can be consumed in the normal combustion process.

EVAP Purge Solenoid Valve
The EVAP purge solenoid valve controls the flow of vapors from the EVAP system to the intake manifold. The purge solenoid valve opens when commanded ON by the control module. This normally closed valve is pulse width modulated (PWM) by the control module to precisely control the flow of fuel vapor to the engine. The valve will also be opened during some portions of the EVAP testing, allowing engine vacuum to enter the EVAP system.

EVAP Vent Solenoid Valve
The EVAP vent solenoid valve controls fresh airflow into the EVAP canister. The valve is normally open. The control module commands the valve ON, closing the valve during some EVAP tests, allowing the system to be tested for leaks.

Fuel Tank Pressure Sensor
The fuel tank pressure (FTP) sensor measures the difference between the pressure or vacuum in the fuel tank and outside air pressure. The control module provides a 5-volt reference and a ground to the FTP sensor. The FTP sensor provides a signal voltage back to the control module that can vary between 0.1-4.9 volts. A high FTP sensor voltage indicates a low fuel tank pressure or vacuum. A low FTP sensor voltage indicates a high fuel tank pressure.

FYI, you should have an Emissions warranty up to 80K

Your EVAP vent valve solenoid is located above the spare tire. Pull out the spare tire and you'll see it. It was like $35.00 at the dealer. When you pull down the spare tire there's a cross member there the valve is on top of that attached to a black metal bracket. The solenoid is canister snapped with 2 hard plastic hoses coming off it. The new one comes with the hoses. The valve looks like a canister. It should be the only thing on top of the cross member if I remember correctly.

Good luck and keep us posted.
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Old 01-22-2011, 12:15 PM
00Sierra 00Sierra is offline
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Thanks for all the information! I'm going to purchase the vent valve solenoid on Monday and will try to put it in Monday night. I'll keep you posted as to my progress.

Rick
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Old 01-24-2011, 10:38 PM
00Sierra 00Sierra is offline
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Does anyone have a part number for the "evaporative vent valve solenoid" for a 2007 Yukon 4wd slt with the 5.3 flex fuel? What about a price? Thanks to all responders!
Rick
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  #7  
Old 01-29-2011, 11:46 PM
00Sierra 00Sierra is offline
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I replaced the EVAP vent valve (not the purge) today on this 07 Yukon tonight. The ACD (AC Delco) Part number is 214-1936 and the GM part number is 25962085. I'm telling you these part numbers because I got the run around from the local dealership parts department. The cost is $32.00 from the dealership. My vent valve was located directly under the spare tire on the cross member. It comes as an assembly and is super easy to install. It took me about 45 minutes including lowering and raising the spare tire. On a scale of 1 to 10 with 1 being the easiest, I would give this job a 2. I have not test drove this vehicle yet to see if the code self clears but I will tomorrow and I will keep you all posted.
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Old 02-10-2011, 10:44 PM
00Sierra 00Sierra is offline
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Sorry it took me so long to reply. Replacing the evap vent valve definitely fixed this problem. I kept waiting for the code to self clear but it never did. I took it back to Advance Auto Parts and they erased the code and for over a week now everything is good! I hope this is helpful to others out there.
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  #9  
Old 03-15-2011, 10:04 AM
finman finman is offline
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Quote:
Originally Posted by 00Sierra View Post
Sorry it took me so long to reply. Replacing the evap vent valve definitely fixed this problem. I kept waiting for the code to self clear but it never did. I took it back to Advance Auto Parts and they erased the code and for over a week now everything is good! I hope this is helpful to others out there.
I just wanted to check to see if this part still solved your problem.

thanks,
Cris
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Old 12-04-2013, 03:12 PM
m4tsby m4tsby is offline
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Sorry to resurrect an old thread but I performed this fix over the weekend on my 07 Yukon and all went well so I thought. Now my wife is saying that each time she has gone to get gas, the pump is cutting her off every minute or so like its full...although its not. She has tried 2 different stations with same results. D

Does anyone know what I may have screwed up?

Thanks for any info.
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