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Randall, ASE Certified Technician
Category: GMC
Satisfied Customers: 12831
Experience:  ASE Master Tech, 32 Years Diagnostic and repair,Electrical specialist
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GMC Yukon: I had my 2005 at Auto Zone on the machine

Customer Question

I had my 2005 at Auto Zone on the machine for the check engine light is on. Gave me error code PO455 Evaporative Emission ( EVAP) System Large Leak Detected, what does that mean?
Submitted: 2 years ago.
Category: GMC
Expert:  Randall replied 2 years ago.
Hello, Engine size?
Customer: replied 2 years ago.
I don't know it buy the vin # ***** *****
Expert:  Randall replied 2 years ago.
thanks, ***** ***** to explain, The likley? you had or have a bad gas cap or was a ittle lose one time, Once code is set, it will not clear on own for a good, bit, You can try removing the NEG battery cable for minimum 90 seconds, this may clear the code , if it returns? then below is some information as well as the possibles. I lean to bad gas cap or one left loose one time beforeA 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 and repair any restriction in the EVAP system.To help locate intermittent leaks, use the J 41413-200 to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT.To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT.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. This may assist in diagnosing the condition.Circuit/System DescriptionThe control module tests for a large leak or restrictions to the purge path in the Evaporative Emission (EVAP) System. When the enabling criteria has been met the control module commands the EVAP vent solenoid valve ON and the EVAP purge solenoid valve ON, allowing vacuum into the EVAP system. The control module monitors the fuel tank pressure (FTP) sensor voltage to verify that the system is able to reach a predetermined level of vacuum within a set amount of time.