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Discussion Starter · #1 · (Edited)
2018 traverse 3.6 awd 110k miles sometimes hard start after refueling. Recently shaking at idle sometimes dying. After doing Google search I thought evap solenoid by throttle body was stuck open. Replaced valve but codes that reappeared are P0442 p0455 p0449 p0171. With a lean code p0171 and solenoid replaced I am assuming a evap hose leak? Anyone have a good idea which one or best way to test and rule out exactly which to replace?
 

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Discussion Starter · #2 · (Edited)
Engine at idle Detached evap hose that connects to purge valve. Checked to see if any vacuum at the side that hooks to metal line while other end connected to valve/solenoid. None.. cleared codes multiple times before rechecking cel. Attaching screen shots of codes and datastream.
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2020 High Country
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Did you use a GM purge valve ? Aftermarket is junk. Only Genuine GM parts on EVAP, sensors, etc. can be trusted.
Check purge valve for black stains or black particles, if you have that then carbon is coming up from the charcoal canister causing valve to stick open.
The 449 is a vent valve issue code.
If purge valve is stuck open and vent valve is open then the 171 will set from the vacuum leak.
STFT on both banks will normally vary between plus and minus 3 if no vacuum leaks.
Engine-Code.com is a good code resource for a quick lookup.
 

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2013 Traverse LT
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I have been having problems with P0442, P0455, and P0496. I started by replacing the gas cap and the purge valve. Each worked for a while but the codes came back. So I decided to replace everything EVAP but the hoses, mainly because the hoses look like special order items.

The vapor canister and solenoid required me to drop the gas tank, which isn’t that bad if the tank is empty. I forgot to reconnect one of the cables, but now everything is up and running. I’ll let you know if the codes come back.

My recent struggles are here:
Dropped gas tank for EVAP now can’t start
 

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FWIW: Regarding code 0455.........Bought a 15 LS with 44k+ in 18. No sooner got it home began setting code 455 ( massive emission leak).. Changed gas caps 87 times....maybe 86. Kept setting that stupid code,is still setting the code,at random. Doesn't effect the running a bit.

So, I just clear the code and keep on going. So far hasn't affected the state's emissions test once a year.

Mite wanna read the "Long, Sad, Sordid tale of Woe, I wrote several years ago, on pulling the "PCV" valve in that beast. Especially when it ain't got one, or so GM says. But, O'REILLYS sells them. Go figure.
 
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