2007 Evap System Issues

[Anelson1122]

My check engine light has been on for 3 years in my 2007 Silverado, reading all of the evap system codes. I have repleaced the vent valve under the hood and the solenoid canister (once without the hose and once with it). The light goes off temporarily and then comes back on. My tag is expired and I can't pass emissions. What else can I try to get the light off?

[daleone3]

Have had the same problem for three years, did all of the same things that you did. I finally bought the diagnostic tool to clear the code and I do so several days before going for my new inspection sticker and it passes every time. I have a 2006, replaced the gas cap the evap unit and the evapp sensor. There was a recall on those to relocate the vent tube but I never did that, there is a longshot that could be it but after trying to fix everything I gave up. There is a sensor for the vent on the gas tank that goes into a charcoal filter, have you checked that

 

 

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[kstruckcountry]

Have you replaced the rectangular canister?

 

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[daleone3]

Not sure if what you are referring to is what I replaced, there is a fuel eve app unit with charcoal filter that runs from the vent on the tank under the bed, that has a sensor built in it as well, I replaced the entire unit. There was a relocation recall on that but I did not relocate it because I did not think it was the issue

 

 

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[Coby7]

What's the remaining code(s)?

[kstruckcountry]

There is an additional canister that is likely clogged.

 

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[daleone3]

There is an additional canister that is likely clogged.

 

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Is that canister under the bed? I do recall replacing the entire unit if that is what you are referring to

Thanks

 

 

 

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[daleone3]

The 07 was a new design from 06. Could be a different configuration

 

 

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[Anelson1122]

I'm pretty sure that was one of the several things I replaced initially.. where do you get the tool to clear the light and how much is it?

[Bob D]

Clearing the code will not help pass emissions.

Inspection computer will "read" that evap emissions has not passed.

(It takes several "driving cycles" for the computer to accept that the evap. system is functioning properly).

[Anelson1122]

The thing is, I'm pretty sure it is functioning properly. The past 3 years just resetting the light has worked and it just comes back on a couple weeks later. This time when I reset it, it came right back on. My tag is already expired so I'm looking for a quick fix for now until I have the money to find out what's really wrong. Someone suggested reprogramming the computer, but it's $150 and not guaranteed to work.

[kstruckcountry]

There should be the solenoid, as well as a rectangular canister.

 

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[Bob D]

The thing is, I'm pretty sure it is functioning properly. The past 3 years just resetting the light has worked and it just comes back on a couple weeks later....

Well if the light comes back on, you can be sure it is NOT functioning properly.

It could be a number of things (including the purge solenoid (easy enough to check)) mentioned above.

Check for obvious leaks; i.e: gas cap, filler neck rust, lines / hoses.

You need to understand HOW the system works to properly diagnose.

Hate to see you throwing money at the problem.

1. When the leak test is performed, the vehicle must have been sitting for at least four to eight hours so that the engine temperature and outside air temperature are identical. There must also be between 15 and 85 percent fuel in the tank—this is to provide a baseline for the test since gasoline and diesel are volatile fluids that expand and vaporize easily with warm temperatures.

2. When the leak test initiates, the Vapor Canister Vent Valve is closed to prevent any fresh air from entering the EVAP system.

3. The Purge Valve is opened, which allows the engine to create a vacuum in the EVAP system.

4. After a specified time interval—usually about ten seconds—the Purge Valve is shut off and the vacuum level in the system is measured by the Fuel Tank Pressure Sensor.

5. Finally, a countdown initiates, which measures the rate at which the vacuum decays in the system. If the vacuum decays much faster than the specified rate or if no amount of vacuum is reached on two consecutive tests, then the Power Train Computer will fail the EVAP system for a gross leak and trigger the P0455 code.

[Anelson1122]

So how has it been able to pass the past 3 years? Yes, the purge solenoid has been replaced twice (once without a new hose and once with it). The only codes I can remember are P0449 and P0496, but every code that came up was the evap system. I guess I can try replacing the rectangular canister. Is this one more difficult to change than the other? I haven't tried replacing the gas cap because the pressure is always fine when my emission test is performed. Maybe I could try replacing it too just because?

[daleone3]

I am in Massachusetts if that helps. Emission testing varies state to state. Search "code clear OBD" and you will see them. Make sure it can clear the code as well as read the code. About 30$

 

 

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