1999 suburban 0440/0440p annoying code

[domer94]

i keep getting this recurring code. there is 135k on the truck , very clean , runs very smooth. ive replaced the gascap twice with genuine GM parts, replaced the evap canister purge valve/solenoid , and replaced the solenoid on the intake next to the throttle body. all hoses an connections look good. at first this code popped up , I cleared it and it would stay away for a couple of weeks. now it is coming back more frequently

any ideas?

 

[SunlitComet]

have you tested the pressure sensor in the tank or the seals/gaskets on the tank attachment points?

 

[domer94]

no I haven't. can you shed some light o exactly what to look for? thanks

 

[99Vortec]

Got any rust on the filler neck?

 

[domer94]

Got any rust on the filler neck?

no, really clean. when I first got this code months ago , when I changed the cap , I really gave attention to the sealing surface of the filler neck.

 

[00Caddy]

Ive replaced everything that deals with this code, except the charcoal canister. Thats next on my list. My p0440 code triggers at random times. Cleared it once and it was gone for 3 months, comes back, cleared it and its back in less than 2 hours. Cleared it and its back in a week. Its completely random. Have replaced pretty much everything you have, even did the gas tank stuff. Replaced the fuel pump and everything while i was in there... The only thing i can think of it being is the charcoal canister on mine. Possible that it could be that on yours as well...

 

[domer94]

good to know. im going to check on prices... love that rock auto