DTC - p0449 & p0440 HELP !!!!

jarhead_jr · November 27, 2006

ok, forgive me if i include too much info here but i need help. 5.3 with 170,000 miles and it still runs strong. i get hard starts when my dtc light is on, p0440 and p0449, when i reset it is starts fine. then the light comes on after a while, (CAN'T FIGURE OUT THE PATTERN TO IT)and it acts up again. i read a page from you guys from april of '05 with a guy , same engine, same prob. you said it wont be the purg valve or the canister, maybe the vent valve or the sensor in the tank. i replaced the fuel pump(new not used), and it of coarse came with all the new components attached. same problem. so i called the dealership for a new vent solenoid, but it comes as a package deal with the new pump that i no longer need. so i went to every junk yard in orlando that had a silverado, and no one wants to get rid of it, once again , with out the pump. on a side note, you'll notice i have a crap load of miles, i drve alot on the highway, so when i fill up, I FILL UP! i'm the guy at the pump squeezing away for every drop, fit 26.8 gals once, they say its a 22 gal tank??? explaine that if you can also.... any way so the possiblity some gas got in the system/canister definatly is there. the truck didnt do this before i went over seas, but it sat for 18 months and here i am. i will try to get the volt reading in the next few days off the pink wire that runs to the vent, IF YOU CAN HELP PLEASE DO SO>>> NO ONE REALLY UNDERSTANDS THIS SYSTEM FOR SOME REASON. MUST BE UNCOMMON. THANKS , JR.

GM-Tech · November 28, 2006

the code p0440 would indicate a faulty purge valve

Where exactly are you getting that information from? Wherever it was, it's mostly wrong. While it may be possible, it is extremely unlikely. A failed purge valve could set a P0440 but you would have purge valve codes along with the P0440. I personally have never seen a purge valve cause a P0440, even when they've failed and are being replaced for other reasons.

A P0440 is a large leak. This could be caused by a vent valve that is not closing/sealing when it should, preventing the system from drawing and holding a vacuum and passing the test. Obviously, it could be caused by genuine leaks in the system (such as something as simple as a gas cap that doesn't seal), but you need special equipment to test for this.

I say replace the evap vent valve and go from there or take it somewhere that can do the proper tests to determine the cause.

GM-Tech · November 27, 2006

P0449 is an electrical problem with the evap vent solenoid and P0440 is "large leak detected" when the system runs the self-test. These tests are only run under very specific conditions, so you may get a light back on in 10 minutes after clearing the codes or 10 days. All depends on the various conditions that have to be met.

Whoever told you the vent solenoid is part of the pump is smoking something really good. The vent solenoid is a totally separate entity and you need to speak to a parts department that knows what the hell they're doing. Either that or you're giving them some misinformation, which might be the case since other places are telling you the same thing.

The P0449 *may* be due to a bad vent solenoid, but it's possible it's a wiring issue. Most likely culprit is the solenoid and if the solenoid is stuck open, you're gonna get the P0440. Pay no attention to the time period needed for the codes to set.

Who told you the capacity of your tank is 22 gals? Short bed capacity is 26 gals. and long bed is 34 gals.

jarhead_jr · November 27, 2006

wow!! great responce time, thanks. let me correct a few things. i understand that the vent valve is not apart of the pump. the chevy dealership said it was sold with the fuel tank, sorry for the typo. i took it a part and cleaned it over the weekend while i replaced the pump, and noticed that it was open while under no power. i read in the repair manual that it was suposed to be closed, so i sprayed some cleaner and pb blast inthere to try to free it up. i doubted the manual because of how the spring was visible from the side in which the plumbing hooks up, it looked like it was a "pushing spring" instead of pulling the "door" shut. sorry if this sounds like mumbo jumbo, but it is def open. what can i expect to see on the voltage if it only opens under such rare conditions? if the purge valve is working correctly and not acting like a vacume leak,why the rought start? sounds like both huh? thanks for your time, really....JR

Discount Auto Parts said it was a 22 gal tank a while ago.. thanks for clearifying. i knew that couldnt be correct.

GM-Tech · November 27, 2006

There is a vent on top of the tank that's part of the tank, but the evap vent solenoid is a different thing. So, maybe they're not understanding what you're looking for. It is DEFINITELY available as a separate piece.

The vent valve should be OPEN to flow when there is no power/ground applied to it. With the key ON, there should be power to the pink wire. The PCM then grounds the white wire as necessary to turn on the solenoid. You could try using an external ground on the white wire when the key's on to see if the solenoid clicks. They usually don't fail electrically but just get full of crud and fail to seal.

Whether or not the vent valve is working, it should not affect the way the engine runs. A stuck open purge valve possibly but not the vent valve.

Usmarine13007com · March 3, 2013

Hello, I have a 2005 Chevy Silverado 5.3l V-8 and have the P0449 code. I was wondering if anybody had a good part # for the Evaporative Emission Control System Vent Valve and Solenoid. I am stationed in cuba and have very little resources down here to get the correct part #'s. Please help.

I found the part on amazon dot com. Ac delco 214-1105 Valve Assembly took me about 2 minutes to install and got rid of DTC p0449.... the cost was about $19 plus shipping

jarhead_jr · November 29, 2006

will do, thanks for the info, you've really been a big help. ill replace the gas cap and vent valve for starters. thanks again.

sledr · November 29, 2006

I had this problem pop up last week. The first sign of trouble was the DIC message "Tighten Fuel Cap" which I did. A few days later the SES light came on. The dealer hooked it up and said it was the Evap canister code. They reset it.

Last night I got the DIC message again and a few minutes later the SES light cam on once again. The light remained on this morning but on my return trip home it turned off - no light. Do I have a bad gas cap as well as an evap canister???

jarhead_jr · November 28, 2006

would you agree that it is quite odd that both would go out at the same time? not very likely for a system that the repair manual lists as something that shouldnt go out durring the service life of the truck? the dtc code p0449 indicates that it is the vent valve, but does not explain the rough start. the code p0440 would indicate a faulty purge valve, and would explain the starting condition, as though there was a vacume leak. but why only when the light is on? if i reset the pcm, it starts fine 100%of the time untill the light comes on again, then it is hard to start untill i restart it again? then it is fine. so i am thinking it is either the unlikely event of both the vent selonoid and purge valve going out at the same time, or maybe a pcm prob? aghhh !!!! the information about the parts to the EVAP system came from a private parts store that "called" the dealership for me, i will call myself to see if their available seperately tom, what do you think about the symptoms? once again thank you for your time, JR.

GM-Tech · November 29, 2006

Do I have a bad gas cap as well as an evap canister???

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I have no idea. Without codes and some diagnosis, I can't even guess.

KRZYKWA · September 23, 2008

Hello, I have a 2005 Chevy Silverado 5.3l V-8 and have the P0449 code. I was wondering if anybody had a good part # for the Evaporative Emission Control System Vent Valve and Solenoid. I am stationed in cuba and have very little resources down here to get the correct part #'s. Please help.