DTC P0440 Evaporative emission system

My TB has popped this code twice now and I was wondering what I should do next.

Anyone have an idea what part it could be? I think it would be what I would know as the EGR (exhaust gas regulator) valve, but dont know what it would be on a GM, or where it is located. Any thoughts would be greatly appreciated. Thanks.

If I am not mistaken, this code can be set due to a bad gas cap or a cap that is missing or not seated correctly.

I would start there... make sure its tight and that when you tighten it that you make it click a few times. The code will go off after a few days of driving.

Or a leak anywhere else in the fuel tank vapor recovery system, or worse, a crack in the gas tank or at the filler neck. Cracked filler necks have been a chronic issue.

Lots of reading here:
http://forums.trailvoy.com/showthread.php?t=22530

Possible coverage under Special Coverage Warranty.

Thanks for the heads up guys. I will be sure to keep an eye on things and maybe take a look at the filler neck for cracks. I reset the code and it has not come back yet.

Just for kicks, I opened the fuel door and low and behold, the gas cap was loose. Not sure how the heck that happened other than maybe the wife didnt put it back on right after a fill up.

On a side not, the info learned on the service bulletin is great to know. Thanks again guy's.

...maybe the wife didnt put it back on right after a fill up..Ahhhhh, the ol' "blame the wife" ploy. OK - we'll go along with that. :yes: We've all used it at one time or another. :thumbsup: ;) ;) :thumbsup:

JK!

My t-blazer is a 2002 LT.

Curious if anyone knows enough about the EVAP system to help answer some questions. For the past month or so I have had the P0440 code come on. I reset it from time to time only to have it return a few days later ( sometimes maybe a week). I was lucky enough to borrow a Snap-on scan tool for a few hours and played with some of the EVAP system controls. One of the items you can do is open/close the Vent valve at the tank ( I could hear the click) and manipulate the purge solenoid (purge %). On my 2002 I was able to increase the purge up to 100% with no noticeable change in the idle of the car. I also noticed what appeared to be correct fuel pressure voltage information for atmospheric (1.5V) increasing as the system pressure changed.

I had the opportunity to run the same test on a 2005 t-blazer and had different results. At ~ 40% purge the engine began to stumble and increasing to 50% and 60% killed the engine.

Can this possible indicate that my purge solenoid is not working properly leading to the differing results ( Assuming that the engine should die under higher purge %) and the code P0440 setting?

Additional info:
- I cannot say that the system maintains the needed pressure that triggers the P0440 but I was able to use the scan tool to pressure the system and verify that releasing the gas cap returned the pressure to atmospheric and had the noticeable sound of pressure equalization while removing the cap. So I am assuming that my cap is okay. I even traded gas caps with the 2005 and did not see a difference in behavior.

I have visually checked the hoses from tank to purge solenoid, unhooked the hoses at the charcoal canister looking for excess loose charcoal particles and did not see any. I do not have a hand vacuum pump so was not able to perform that test.

I have read about the extended warrantee on the EXT versions but mine is a regular LT so I am unlikely to be covered.

Several items differ in the 2002 vs. 2005 versions. My 2002 code list does not include the more details 442,443 etc codes indicating small or large leak. The 2005 did have those codes. Also the 2005 has a dash idiot light that indicates a loose gas cap, my 2002 does not even though my 2002 is better equipped. (2005 was an LS).
The charcoal canister on my 2002 is above the frame rail right behind the drivers door. The 2005 was mounted over the fuel tank and I did not see a fuel filter on the 2005.
:bonk:
Ok TMI.. but any help with the questions would be appreciated,

I never heard from any of the knowledgable folks on my previous posting, but it turns out I was closer then I thought.

The key to the test was the purge solenoid % that did not trigger the engine stumble. I had to take it to the dealer and pay them to run the entire EVAP system test and guess what they concluded... Purge Solenoid was malfunctioning...

So FYI to those still looking for a solution. I was faced with throwing parts at the problem or letting the dealer use their diag tools to find the real problem... . Fixed now.... for a $30 part that ends up being $180. :hissy: