Check Engine Light - Emissions Control

[ranger952]

Hi all,

I have my check engine light on. I had the code run, and it's a P0440. That comes back to the Evaporative and Emissions control system.

I have had this code cleared twice and it comes back. I am NOT, repeat, NOT leaving the gas cap loose. Something else is going on.

Any ideas? Is there a vent tube for the gas tank or soemthing that I should look at?

I heard that there may be a solenoid control down on my gas tank or emissions system somewhere that can go out.

Also, the light does not stay on all of the time. It does go out for a little while, but definetly stays on longer the next time. So, I do beleive something is going on.

Please help!!! :-)

Thanks.

[Shaners]

Could your gas cap be faulty? That's not really too uncommon...

 

I believe there is a charcoal evaporator canister or something like that connected to the fuel system.

[Cool Zr2]

Is your gas cap loose?

[Sierra54]

I had a similar problem which turned out to be a faulty vent. I believe it was diagnosed by putting smoke in the fuel lines to find the faulty vent. This was awhile ago, sorry I can't recall much more. But I had the service engine light come on and a diagnosis similar to yours.

I hope this helps.

[ryan632]

i currently have the same problem with mine and its not the gas cap cause i replaced it

[covvy]

Well this code is set when the truck checks the EVAP (gas tank and such) system for leaks. The gas vapors are trapped in the carbon canister then tranfered to the intake plenum. If the tank pressure rises about a set value in the system, the gas tank has a vent solenoid on top to vent the pressure or if the system needs to be purged then it also opens this valve. If any cracks apear in any lines (purge lines, filler neck vent line, carbon canister) or the vent or purge solenoids fail then the MIL light will illuminate. There is varry little someone can do without dedicated tools like a smoke tester on regulated air pressure to find the flaw. I'm not sure where on your truck the vent valve is but if it acsessable then you can remove it and try to blow through it. If air passes through the valve then apply power and ground to the terminals and try again. Air should not pass. (the opperation may be reversed I can't remember but one way air should pass and not the other) Good luck hope this helped.

[99-2door]

The evap canister and valve are located on the frame near the gas tank on NBS trucks. On OBS trucks they are on the core support near the left front corner.

[ranger952]

It seems that the problem might be the "vent". I have taken the gas cap off when the truck is off, and let it vent for a min. I put the cap back on, and viola! the light goes off.

I bet it is the solenoid or vent or both?

I have a 98 silverado, 1500, 5.7. Any idea where I need to start looking? I did replace the gas cap two weeks ago.

[ness5575]

when my ses light came on, i got the same code. i tried a new gas cap first but it didnt work. took i to the dealer (ext warranty) and they replaced the evap system solenoid valve. that did the trick.

[ranger952]

Thanks Ness. I think I will try that.

[digital]

I just had my truck scanned, had the same problem, throwing the code for the EVAP Canister...

 

The truck was under extended warranty, took it to the dealer, they said that the wire was un-plugged. They plugged it back in and still had the nerve to charge me the $80 "Diagnostic Charge".....

 

Anyways, I thought I would also let you guys know that this is the first time that I had to smog my truck with a Whipple Supercharger, JBA Headers and Flowmaster muffler and it passed with cleaner numbers than a stock 2000 Silverado 5.3..I was surprised!

 

Matt