P0455 code troubleshooting

[ReaperHWK]

Have this code intermittently. It’s an EVAP large leak. I already:

1)replaced gas cap with OEM
2) checked fuel line between gas tank and filler.

I’ll still get the code to come on and clear itself. I also get the “tighten gas cap” message at time as well.

Anything else I should check that’s obvious before I start digging into this more?

 

[Fless]

FWIW my first guess would be an intermittent vent valve, or purge valve. Both relatively inexpensive and easy to change proactively, but also can be tested and diagnosed before throwing parts at it.

 

[strutaeng]

Try this:

P0455 — 2006 Chevy Truck Suburban 3/4 Ton 2WD V8-6.0L VIN U Service Manual | Operation CHARM

Detailed repair manual for the 2006 Chevy Truck Suburban 3/4 Ton 2WD V8-6.0L VIN U.

charm.li

 

[Doubeleive]

the sucky part is evap testing is difficult at best
it has to be done just right and when cold and if you mess up in the process, you have to wait and start all over again hours later after it has cooled back down
the vent valve is probably the easiest to test (the one on the engine) but it is also only $30 for a new oem one
the evap canister is $130
the vent solenoid is around $65
I usually just tell people to shotgun it (replace all ) and be done with it.

 

[ReaperHWK]

the sucky part is evap testing is difficult at best
it has to be done just right and when cold and if you mess up in the process, you have to wait and start all over again hours later after it has cooled back down
the vent valve is probably the easiest to test (the one on the engine) but it is also only $30 for a new oem one
the evap canister is $130
the vent solenoid is around $65
I usually just tell people to shotgun it (replace all ) and be done with it.

For those prices are I’ll just replace it. Is that the order I should replace?

 

[Fless]

the sucky part is evap testing is difficult at best
it has to be done just right and when cold and if you mess up in the process, you have to wait and start all over again hours later after it has cooled back down
the vent valve is probably the easiest to test (the one on the engine) but it is also only $30 for a new oem one
the evap canister is $130
the vent solenoid is around $65
I usually just tell people to shotgun it (replace all ) and be done with it.

No vent valve on the engine, it's a purge valve there. It sucks. With vacuum.

 

[Doubeleive]

No vent valve on the engine, it's a purge valve there. It sucks. With vacuum.

I always forget technically what it's called that's what it shows it as on rockauto

 

[Doubeleive]

For those prices are I’ll just replace it. Is that the order I should replace?

the one under the hood is pretty easy, the rest are up under the spare tire area by the gas tank
I would think the canister on a 2015 would still be fine, but no telling I replaced mine on my 2012 already
started getting the tighten gas cap crap and knew then it was time to do it.
it takes time for it set as well when you replace something and clear the code it normally takes about 3 days to see if the code stays away or not.
if you make it past 3 days and no code the chances are good you nipped it.
I would highly recommend oem parts in any case, the aftermarket ones tend to fail in no time at all

 

[Fless]

the sucky part is evap testing is difficult at best
it has to be done just right and when cold and if you mess up in the process, you have to wait and start all over again hours later after it has cooled back down

The procedure for testing is not that difficult with a decent bidirectional scanner. Even an inexpensive scanner can show the fuel tank pressure, which is a major part of the test data. A purge and seal test can show a lot, if you want to do actual diagnostics. If that's not right for your situation, do the parts and pray.

You're correct about the onboard emissions system test being finicky about the testing conditions.

What Is The Purge/Seal EVAP System

The most common EVAP system where uel vapors are stored in the fuel tank and the vapor canister.

gotech.com

Near the end of this video Eric O shows the purge and seal test, and how to understand the fuel tank pressure and vacuum decay.

MORE: Mike at Wells does a great job of explaining and testing:

 

[ReaperHWK]

The procedure for testing is not that difficult with a decent bidirectional scanner. Even an inexpensive scanner can show the fuel tank pressure, which is a major part of the test data. A purge and seal test can show a lot, if you want to do actual diagnostics. If that's not right for your situation, do the parts and pray.

You're correct about the onboard emissions system test being finicky about the testing conditions.

What Is The Purge/Seal EVAP System

The most common EVAP system where uel vapors are stored in the fuel tank and the vapor canister.

gotech.com

Near the end of this video Eric O shows the purge and seal test, and how to understand the fuel tank pressure and vacuum decay.

MORE: Mike at Wells does a great job of explaining and testing:

I did notice my scanner has the EVAP test. I tried to run it but the coolant was too hot it said. Seems like a ton of conditions needed to do it. Maybe I’ll look into it more.

But my car is 9 yrs old maybe it’s better just to replace this crap?

 

[Fless]

Define "better." LOL It's whatever you feel like doing!

 

[Doubeleive]

I did notice my scanner has the EVAP test. I tried to run it but the coolant was too hot it said. Seems like a ton of conditions needed to do it. Maybe I’ll look into it more.

But my car is 9 yrs old maybe it’s better just to replace this crap?

ever since the first time this crap came up for me and trying to troubleshoot it back years ago and having no luck and mechanic saying "can't find it"
I just replace all three parts and be done with it. a person could go get a diagnostic and mechanic can say yes it's this part that will be $250 please
and 3 days later the code is back and now the mechanic wants more money f-that.
this last time with the tech2 I tried to do the "evap test" the problem I ran into was keeping the rpm between 2k-4k and almost getting it and then accidentally go under/over and now it's too hot...... it's like loosing a video game and no more quarters, try again later lol.
30-40 minute job and done.......for another 10 years

**then if the evap canister gets too old the dam pellets come out and get stuck in the lines so that just adds headache to misery

they changed the system I think in 2016? to a capless gas tank, not sure if that is going to make a difference with the evap issue's or not, these 2015's are just getting to that age.

next up will probably be the heater hose t's, the ones on the wifes 2016 are not looking very healthy and the heater hoses like to seep they changed how they are crimped, not as good as the ones on the 900's

 

[Fless]

ever since the first time this crap came up for me and trying to troubleshoot it back years ago and having no luck and mechanic saying "can't find it"
I just replace all three parts and be done with it. a person could go get a diagnostic and mechanic can say yes it's this part that will be $250 please
and 3 days later the code is back and now the mechanic wants more money f-that.
this last time with the tech2 I tried to do the "evap test" the problem I ran into was keeping the rpm between 2k-4k and almost getting it and then accidentally go under/over and now it's too hot...... it's like loosing a video game and no more quarters, try again later lol.
30-40 minute job and done.......for another 10 years

**then if the evap canister gets too old the dam pellets come out and get stuck in the lines so that just adds headache to misery

Agreed. If you can diag it yourself, or just replace the parts and it works, then you're money ahead.

Mine was a bit more difficult but -- after replacing the canister and both valves -- it turned out to be a bad gasket on the fuel pump. I did the purge and seal test (not any "evap test" whatever that is) to verify that there was a leak, and we used a makeshift smoke machine to find it. In my twisted mind I wanted to know for sure what caused it.

 

[Doubeleive]

Agreed. If you can diag it yourself, or just replace the parts and it works, then you're money ahead.

Mine was a bit more difficult but -- after replacing the canister and both valves -- it turned out to be a bad gasket on the fuel pump. I did the purge and seal test (not any "evap test" whatever that is) to verify that there was a leak, and we used a makeshift smoke machine to find it. In my twisted mind I wanted to know for sure what caused it.

when it passes a smoke test, but is still failing it's gets pretty frustrating. because now you have spent money to "fix" the problem and still have to spend more money to "fix" the problem. especially when you don't have money to just toss around.
had a tire & wheel like that once on my 03, slow leak, take it to the tire shop to fix, can't find a leak. 3 days later tire flat as a pancake, fill it up, 2 days later it's almost flat again, fill it up. "stops leaking" wtf??????? lol only thing I ever figured was maybe it was something in the seam and only leaked with a load on it and whatever it was it fixed it's self

 

[NardDog]

i had this happen a fee years ago and wound up replacing all the valves and canister. No problems since but I suppose could have tried to diagnose but i just figured its still cheaper to diy all the parts than to pay a shop to do it.

 

[ReaperHWK]

the one under the hood is pretty easy, the rest are up under the spare tire area by the gas tank
I would think the canister on a 2015 would still be fine, but no telling I replaced mine on my 2012 already
started getting the tighten gas cap crap and knew then it was time to do it.
it takes time for it set as well when you replace something and clear the code it normally takes about 3 days to see if the code stays away or not.
if you make it past 3 days and no code the chances are good you nipped it.
I would highly recommend oem parts in any case, the aftermarket ones tend to fail in no time at all

Are these the correct parts?
There are 2 vent valves for my truck, which one do I need or I need both?


Evap canister:

2004-2017 GM Vapor Canister 15109431 | TascaParts.com

2004-2017 GM part # 15109431 - Vapor Canister

www.tascaparts.com

Vapor canister vent valve:

2007-2018 GM Vapor Canister Vent Valve 23481275 | TascaParts.com

2007-2018 GM part # 23481275 - Vapor Canister Vent Valve

www.tascaparts.com

Vapor canister vent valve:

2014-2025 GM Vapor Canister Vent Valve 12630282 | TascaParts.com

2014-2025 GM part # 12630282 - Vapor Canister Vent Valve

www.tascaparts.com

 

[Fless]

The 2014-25 "vent" valve is mis-labled. That's a PURGE valve and it goes on the engine. I don't know if they'd be correct for your vehicle.

 

[Doubeleive]

Are these the correct parts?
There are 2 vent valves for my truck, which one do I need or I need both?


Evap canister:

2004-2017 GM Vapor Canister 15109431 | TascaParts.com

2004-2017 GM part # 15109431 - Vapor Canister

www.tascaparts.com

Vapor canister vent valve:

2007-2018 GM Vapor Canister Vent Valve 23481275 | TascaParts.com

2007-2018 GM part # 23481275 - Vapor Canister Vent Valve

www.tascaparts.com

Vapor canister vent valve:

2014-2025 GM Vapor Canister Vent Valve 12630282 | TascaParts.com

2014-2025 GM part # 12630282 - Vapor Canister Vent Valve

www.tascaparts.com

those are the parts but those same parts are a lot less on Rockauto, plus you get 5% off with a code that is listed on the forum all the time, which sort of helps with any taxes.

 

[ReaperHWK]

those are the parts but those same parts are a lot less on Rockauto, plus you get 5% off with a code that is listed on the forum all the time, which sort of helps with any taxes.
View attachment 442315

Great thanks. I’ll order these 3 items from rock auto.

 

[Fless]

There's a current discount code on this thread:

Rock Auto Discount Codes - Post 'em Here for Others to Use

Code: 340980136269906521 Expires July 10th

www.tahoeyukonforum.com

When you are ordering, enter that code in the "How did you hear about us?" field.