P 0440 code

I had my intake gaskets replaced due to antifreeze leaking....about a week after the service engine soon light came on.....the shop said to bring it back....well the light went out so I did not go back.....then it came on again and I was going to call but as soon as I thought about it, it went out again....guess what its back....it has been 3 weeks.....

One thing I have noticed is it seems to come on after I fill up...within 2 days...and when I get down around a qurter tank it goes out.....

I have replaced the gas cap....anybody have any suggestions?

P0440 covers every component in the EVAP system: fuel tank, EVAP vent solenoid, fuel tank pressure sensor, fuel level sensor, vapor lines from the tank to the canister, purge lines from the canister to the engine, the canister itself, EVAP purge solenoid, fuel cap, fuel filler neck etc etc. The fact that it covers so many components makes diagnosis difficult and time consuming, even by a professional using expensive specialized test equipment. The diagnostic flow chart in the GM shop manual involves 4 pages of diagnostics. Replacing the fuel cap with an AC Delco cap is a good place to start. You can check for loose connections in the filler neck and vapor lines, but if that turns out ok, you'll probably have to bite the bullet and have a pro look at it. Make sure they are familiar with EVAP system diagnosis and have the proper equipment.

Thats what I was afraid of.....its wierd that it started right after the shop replaced my lower intake gaskets though...so I am guessing its somewhere under the hood....I have looked but do not see any cracked hoses or loose lines.

friesza
Did you ever figure out what was causing your code to appear? Ever since I had a replacement engine put in my sons 96 S 10 Blazer I have the same problem. They replaced the intake manifold gasket at the same time also. Im like you and figure it has something to do with a cracked hose or something under the hood. I also tried gas cap. My son never fills the car with more then $10.00 or $20.00 of gas. Ill have to have him fill it and see if it still happens. Let me know what you found. Thanks.

Keep in mind, the ECM will only run the EVAP monitor when the fuel level is between 15% and 85%.

The funny thing is...whenever I plan on taking it to the shop...the light goes out.....it is weird....it would go out at 1/4 tank then come on after fill up...it doesnt do that anymore...just a random check engine light every week or so...and with my work schedule almost impossible to get somewhere to have it checked.....I am going to look thoroughly over the hoses tommorrow...