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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), GMC Mechanic
Category: GM
Satisfied Customers: 5787
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Is this cost anything? 2005 GMC Yukon Denali, yes...Getting

Customer Question

is this cost anything?
JA: What is the model/year of your GM?
Customer: 2005 GMC Yukon Denali
JA: Are you fixing your Yukon Denali yourself? What have you tried so far?
Customer: yes...Getting a P0455 code, have replaced the gas cap and the evap canister already.
JA: Has the vehicle turned into a gas hog? And how does it start -- same as usual?
Customer: not sure about fuel and seems to start fine... had code cleared and tried to pass emissions but did not pass
JA: Anything else you want the mechanic to know before I connect you?
Customer: not that I can think of
Submitted: 10 months ago.
Category: GM
Expert:  TODD RUZICKA replied 10 months ago.

Hi and thank you for the question. My name is ***** ***** I'll do my best to help. A P0455 is a large Evaporative emissions system leak detected code, as you most likely know. The most common issue is the gas cap, which you replaced. The best way to have this properly diagnosed, is to have your local shop or dealer perform a "smoke" test on the Evap system. Has any other work been performed on the vehicle prior to the light coming on?

Expert:  TODD RUZICKA replied 10 months ago.

We couldn't connect unfortunately via a phone call, it just rang...would you like to try again?

Expert:  TODD RUZICKA replied 10 months ago.

Please accept my apologies, the previous message was to a different Denali customer...

Customer: replied 10 months ago.
before all this started we replaced the water pump and the oil sending unit.
Expert:  TODD RUZICKA replied 10 months ago.

Ok good to know. Have you checked any / all of the evaporative emissions lines on or around the engine to make sure one of the vacuum lines was not left disconnected?