P0440 headscratcher

[EHB]

this code has plagued me the entire time i've owned the car.(december) i've had a buddy hook his scanner up and shut it off about 4 times. actually found a broken vacuum line at the TB and fixed it with the scottydogg method. code popped back up a few days later ...
the cel seemed to be pretty random as far as how long it took before it popped back on...
then i had an epiphany and finally thought i found the common denominator. the light came on when i got gas. first i thought it was because i filled her up like a nascar pit stop. fill it till it runs back out. figured thats the most accurate way to calculate fuel mileage right ?
well the last time i got gas i DIDN'T jam her full. i filled her up to 3 quarters ...light popped on soooo......
So i get the light shut off AGAIN , been off for 80 miles or so or about 8 days . i re examed my cap again today which seems ok to me , and i look at my brothers car and checked his cap and it was the same style... woohoo !!! just saved myself the $13 bucks a new one would cost me which might not even be the problem..so i planned on swapping them. ( don't judge his lights on any way and his vehicle is a hunk of **** and he don't care )
well i tried his cap then put mine back on and felt no difference as far as feeling tight so i didn't steal his.
next time i start the car , damn light pops on ... but wait... i didn't get gas ...

so now i know it's just REMOVING the cap that causes the evap leak.
so here's my confusion. obviously the cap does seal or the light would always be on... right ? is it just really slow at pressurizing ? help me out here fellas.

[BillBoost37]

Do you turn the engine off when you fill up?

[mguzzo]

you may have a pinhole leak in the filler tube between the gas cap and the tank. The PCM will close the solenoid to isolate the eval canister then use engine vacuum to apply cvacuum to the tank the tank and looks for a pressure change and hold. so if you have a hole the pressure won't hold and it will pop the code.

[EHB]

Do you turn the engine off when you fill up?

yes ...but i don't even need to put gas in the tank to make the code pop on ... removing the cap alone will set the code.

[EHB]

the gas tank , filler neck , and all fuel lines from the tank to the engine were installed brand new in march. if the light is turned off it doesn't come back on until after i take the cap off so it must hold pressure until i remove the cap at least.

[EHB]

nobody has any suggestions ?

[Scottydoggs]

if you leave the cap loose the code will come on. if its not taking gas theres a issue with the canister tank or the maybe the fill hose is blocked up.

your tank is under pressure, it knows when its not and throws the code.


your not supposed to fuel up a running car anyways. its kinda a law.

[EHB]

if you leave the cap loose the code will come on. if its not taking gas theres a issue with the canister tank or the maybe the fill hose is blocked up.

your tank is under pressure, it knows when its not and throws the code.


your not supposed to fuel up a running car anyways. its kinda a law.

i twist the cap several times so it's as tight as it get with those style caps. if it was a matter of a lose cap then why whenever the code CEL is turned off , it doesn't come back on until the cap is removed and put back on again. as i said , putting gas into the car is NOT the Xfactor. simply taking the cap off and putting it back on throws the code at next start up.
now if i shut the light off , it won't come back on till the next time the cap is removed again. so apparently it's holding pressure but the light won't go off unless it's manually turned off. maybe it takes to long to build up pressure ?
i DO NOT fuel up when the car is running.

[bandook]

When I was looking up the different pcm bins that GM provided for my car...forgot which site I was on but it shows all the updated bins that GM used...I noticed one of them was specifically noted to correct the evap code from falsely tripping the CEL. I'll see if I can find that site again.

Have had the evap codes popping up as long as I've had this car, bought it off my mom and she has always had it. Replaced many things and it still comes up, well...used to until I got dhp.

[Scottydoggs]

whats a evap? yup like 10 codes later its fully deleted.


you try a new gas cap yet? maybe its a leaking.

[bandook]

whats a evap?

P0440
What does that mean? This indicates that a part of the EVAP control system is no longer fuctioning correctly. The EVAP system consists of many parts, including (but not limited to) the gas cap, fuel lines, carbon canister, purge valve, and other hoses The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.

Read more at: http://www.obd-codes.com/p0440
Copyright © OBD-Codes.com

[Scottydoggs]

i know what a evap is, it no longer exists on my car. fully deleted.

[bandook]

i know what a evap is, it no longer exists on my car. fully deleted.

Dude, I was freaking out wondering why you asked lol. I was like, I know he knows but maybe he's having a senior moment. Or the yellow paint inhalation was getting to you. Sorry, your comment went right over my head. Happens so often I should be wearing a large Indian headdress to knock some down.

[Scottydoggs]

lol

[HighOctaneRacing]

This thread is funny as hell hahha