you have to use a scanner to reset the codes and its not going to check it for a certain number of "drive cycles" which maybe a while or tomorrow hard to tell. you pretty much need a reader to work on 96+ vehicles but its become cheap. and the cheap ones will read codes and erase thats the most basic function. the more expensive ones have more onscreen info, more ability to read live data like sensor outputs etc. the one i have been using is the torque pro app for android its $5 and links to the car with a obd2 bluetooth adapter that can be as low as 30-40 depending on how fast you wan it to be. i have a $150 one i dont use anymore because this does twice as much.

as far as the vent valve thats an educated guess i work on many different gms for my family and friends and it seems the majority of the time on 2000+ the vent valve is the issue. its how the air gets out when you pump and that and also what has to be able to seal for the large and small leak tests among other things. the filter get filled with crap and the silt, salt and other junk gets into the solenoid and it cant move or cant seal. so i go there first take it out try blowing through it with some wire jumpers like mentioned above

Hey Mike, thanks for the info. I will keep a eye on it the next coupe of days. If it was the gas cap that was causing the light to come on, would that affect my bad gas milage I have been having?

I can't say for sure really. Hmmm, quick Google search.

http://articles.cnn.com/2008-04-09/l...l?_s=PM:LIVING

If I understand this correctly, allowing fuel vapor to leave a container allows the fuel itself to break down. Which would cause poor fuel economy. So, yea.

As of today it is still coming on. Ive started it at least 4 times sence puting on the gas cap.

I just looked up that P0440 on Alldata.
On my 2000 Blazer:
On my 97 Bonneville:
.

These values may not exactly fit your car, but it is to give you a rough idea what it takes to get this code to clear on its own. You could always ask Autozone to clear it for you.

I read that a bad vent valve would pop up the code P0446. Would it still be a issue sence my code was P0440?

Also, I noticed that after I put on the new gas cap that the car would wouldnt feel like its draging anymore. When I hit the gas peddel it took off better then before. Would the gas cap be a issue with the way it runs?

the vent valve would have to fail electrically to set 446. any kind of leak in the whole system can cause this. one time on my 3800(its a 98 so im not sure if its the same) the boot where the vacuum lines for the purge valve and fuel pressure regulator started getting brittle and that caused both 440 and drive-ability issues, because its a big vacuum leak and the fpr isnt getting the proper signal. you could start the engine and spray tb or carb cleaner around there and see if the engine changes pitch as you spray that area.

P0440 EVAP System No Flow During Purge Possible Causes Setting Conditions

Charcoal canister is loaded with fuel or moisture
Fuel filler cap is loose, cross-threaded, damaged or wrong part
Fuel tank, fuel filler neck or fuel sending unit 'O' ring is leaking
Fuel tank pressure sensor is damaged, disconnected or it failed
Fuel tank vapor line(*) is clogged, damaged or disconnected
Purge valve vapor line is clogged, damaged, or disconnected
Purge or vent solenoid power circuit is open (check the fuse)
PCM has failed

Where would the fuse be for the Purge or vent solenoid power circuit? Iv'e been thinking about checking the fuses. I see there is a fuse box in my glove compartment and there is a big black box next to the battery that has fuses in it. That remindes me to check my fuse (if there is one) for my wiper fluid that stopped working the other day. The wipers work but no fluid..Im not to worried about that right now tho...

Do the vacuum lines for the purge valve and fuel pressure regulator go up to the engine that fits onto a round looking bell shaped thing?