'Tighten Fuel Cap' creating a P0455 DTC

[h_d_ryder]

2004-2006 Tahoe. Has anyone had a 'Tighten Fuel Cap' message that ends up creating a P0455 DTC, and tightening or replacing the cap does not correct the problem? Did you find your EVAP leak?
So far I have replaced the Fuel Cap, vapor canister vent valve solenoid and attached hose, and vapor canister purge valve solenoid.

 

[Scottydoggs]

Time for a smoke test, the 455 is a large leak, so you'll see the smoke easy.

 

[h_d_ryder]

I have a home made smoke machine. Where do you suggest I have the input line into the system? At the fuel cap location, or is there a better location?

 

[Scottydoggs]

gas cap works, or pull the evap line off the engine and smoke it from there.

 

[PNWYukon]

• A fuel fill cap that is left OFF after a fuel fill will cause this DTC to set.
• A loose, missing, or damaged fuel fill cap can cause this DTC to set.
• A blockage or restriction in the EVAP purge solenoid, purge pipe EVAP canister, or vapor pipe, can cause this DTC to set.
• A temporary blockage in the EVAP purge solenoid, purge pipe, or EVAP canister could cause an intermittent condition. Inspect/repair any restriction in the EVAP system.
• To help locate introduce smoke into the EVAP system. Move all EVAP components while observing smoke.
• To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles.
• Observe the Freeze Frame/Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition occurs that caused the DTC to set.