BostonKev

Hi all, my wife got a check engine light on the Impala and the code says it's a 0440. I read what it says it is but any suggestions on things to look at would be appreciated. Thank you

bigrod118

P0440 - Evaporative Emission (EVAP) System

Basically, you have a small leak somewhere in the EVAP system. The most common place to check, is the gas cap. Go and retighten it down, get the code cleared, if it comes back, buy a new cap and try again. New gas caps are cheap, so that would be the best place to start. If that doesnt fix it, well, I don't know, cuz it's always been taht for the majority of people.

BostonKev

you probably will have a tough time believing this but my wife says she went and got gas right before the check engine light came on. Doesn't that sound extremely odd? I appreciate your help. Thank you

bigrod118

Nope, that doesnt sound odd at all, whenever people get taht code, that is generally exactly what they say. She may have just forgotten to tighten it down enough, or the cap is going bad.

JJ Newel

I got the same code and the mechanic couldn't fix it. Had the gas cap tested and that wasn't it, so I gave up on that.

BostonKev

Ok so I replaced the cap amd it still comes on roughly a day and a half after I reset the code. Any other suggestions on things to look at? I appreciate your help.

richtazz

Does your wife normally drive the car? Does she tighten the cap to at least three clicks like she's supposed to? What brand of cap did you buy, AC-Delco or aftermarket? Check the fuel filler hose and vent tube for rust holes or dents/cracks. It could be anywhere from the tank to the purge canister, so if it's not readily apparent, you may have to take it in and have it checked.

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Would you drive any better with that cell phone up your ...?!

ysteve

OK guys. Maybe you gonna laugh but i saw somwhere and its came out CAT. I dont remember where, try pages around 25-40 somewhere overthere.
Check exhaust pressure supostube 1,25 PSI. Good luck!!!

bigrod118

well, there are a few components of the EVAP system, not a lot, but I dont know how much they cost on average, so I dont think just replacing them 1 by 1 is going to be your best bet.

you may want to just take it to the dealer and have them read the code, they can figure out exactly what part is failing, then you wont have to replace un-nessecary parts.

BostonKev

I grabbed another GM cap from a junkyard and reset the code. The CEL light came on about a day & a half later. Then mysteriously the light went off after I took the car on the highway and it's been about 2 days and it hasn't come back on. I'm confused but I appreciate the help.

bigrod118

Well, to help with some confusion...

when something goes wrong with your car, and it can throw a DTC, your car has to go thru 3 cycles in a row, for it to "accept" the DTC, then it will show you a light. A cycle means, your car has to go from a cold start (below 140 I think) all the way up to operating temp (about 180 - 190) then back down to below to the cold start. It has to do that 3 times until it will show you a light.

so once you reset the light, thats why it took a few days until it came back on. also, I fairly sure, that the light went away for the same reason, just took a few cycles for it to realize it was fixed.

then again it could still come back, either way I still stick with my last suggestion about going to the dealership to have them pinpoint the problem.