p0455 evap large leak or no flow. (check gas cap)

[blazerk5drew]

Thought I would share my story on the p0455 issues with my 2005 tahoe. Usually this tells me that I have a leak in the evap system and to inspect things like gas filler neck, gas cap, canister, operate purge/vent solenoids. I was lucky enought to borrow a smoke machine to try and find the leak. after 45 minutes of laying under the truck with no signs of any leak I found that the vacuum elbow at the pcv valve was cracked and leaking terribly. After changine the elbow and clearing the codes I no longer have any evap codes or tighten gas cap messages after burning two tanks of gas. I have seen people throw every part at the evap systems on these trucks with no success. Sometimes we forget simple things like vacuum lines (truck is almost 9 years old). I hope someone searches for this one day and finds it helpful.

 

[TxTooTall]

there's a purge valve on top of the intake. you can pull it off and try "blowing" into it. When it has no power, it should be in the closed position.

 

[Mechahead]

Yeah, I diagnose evap leaks often and sometimes still forget to check that the system is actually getting vacuum in the first place. Real easy to pop up as a gross leak if there is a vacuum loss on the engine. I check with it in seal mode and if my smoke machine shows its holding more than 10 pounds, I go to the other side of the system and smoke the intake.

 

[Covert One]

Thought I would share my story on the p0455 issues with my 2005 tahoe. Usually this tells me that I have a leak in the evap system and to inspect things like gas filler neck, gas cap, canister, operate purge/vent solenoids. I was lucky enought to borrow a smoke machine to try and find the leak. after 45 minutes of laying under the truck with no signs of any leak I found that the vacuum elbow at the pcv valve was cracked and leaking terribly. After changine the elbow and clearing the codes I no longer have any evap codes or tighten gas cap messages after burning two tanks of gas. I have seen people throw every part at the evap systems on these trucks with no success. Sometimes we forget simple things like vacuum lines (truck is almost 9 years old). I hope someone searches for this one day and finds it helpful.

The same issue was on our 2005 Chevy Tahoe. We found a P0455 problem code and searched for a solution on line. I found your post and looked at the hoses around the PCV valve line. That was the problem as the rubber hoses deformed and allowed air to get pulled in through the vacuum system. I replaced both flexible ends with 5/16" fuel line and cleared the error code.

The error code stayed cleared.

Now, I looked at the same error code on my 2007 Chevy Silverado and, yes, one of the rubber hose connections was cracked!

Long story short: check the hoses and rubber connections first before changing parts.

 

[treehan77]

can anyone snap a pic of where the hose was leaking? Also-Does your 05 have a replaceable PCV?