P0455 code troubleshooting

ReaperHWK · Nov 3, 2024

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 · Nov 3, 2024

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 · Nov 3, 2024

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 · Nov 3, 2024

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 · Nov 3, 2024

Doubeleive said:
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 · Nov 3, 2024

Doubeleive said:
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 · Nov 3, 2024

Fless said:
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 · Nov 3, 2024

ReaperHWK said:
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 · Nov 3, 2024

Doubeleive said:
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 · Nov 3, 2024

Fless said:
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?

P0455 code troubleshooting

ReaperHWK

Full Access Member

Fless

strutaeng

Full Access Member

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

Doubeleive

Wes

ReaperHWK

Full Access Member

Fless

Doubeleive

Wes

Doubeleive

Wes

Fless

What Is The Purge/Seal EVAP System

ReaperHWK

Full Access Member

What Is The Purge/Seal EVAP System

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