Question about 2005 GMC Yukon Denali

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I have a 2005 Yukon Denali with 66K miles. For

I have a 2005 Yukon Denali with 66K miles. For the past few weeks I get a flashing check engine light on the highway (intermittently) between speeds of 65-80 mph. The light flashed, the engine shakes and hesitates. The light remains flasing for 1-5 minutes, then as I go below 65, disappears. Fuel?? Exhaust?

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Sounds like a missfire, probably spark plug wires they usually go bad before the plugs anymore. You can take it to one of your local parts stores and have them pull the fault code that is making the light come on. If it shows a missfire then a good tune-up should take care of it. Hope this helps

Posted on Jun 25, 2009

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I had the same problem with my ’02 Denali and I took it down to a local shop yesterday to have a $60 computer diagnostic test done. They told me the catalytic converter was backed up and causing the misfire at high RPM. Easy fix. $230 later they put a new cat which did the trick. They also suggested a tune up (new plugs, wires, air filter, and fuel filter) which I will do myself tomorrow.

The shop also told me that by law, a catalytic converter has to be warranted my law for 80,000 miles. My problem was that I had 81,000 miles. I called some GM corporate number to see if they would plead my case ( told them the situation and wanted to see if they could offer some sort of GM business goodwill that they would “write off” and apply to my situation) They said all I had to do was take it to a GMC dealer and have it diagnosed for $100 and they could forgive me. The shop owner and his son highly suggested I get it done there since it would be covered but it was not convenient for me to drive across town to save a measly $130.00. Plus I really like the work this “mom and pop” shop does and value their honesty.

Here’s a little side info. The GMC dealership said that if it wasn’t covered under warranty, it would have been $900-1100 to change the catalytic converter. WOW! A much different price compared to what the local shop charged me.

Anywho, this post is getting rather lengthy but I saw you were having the same (or similar) problem and thought I’d share my experience in hopes that it might help. Just remember, the computers in today’s vehicles record EVERYTHING you do while driving your truck, from the top speed you drove to work this morning, to an engine misfire. The computer diagnostic will save you time and money by pinpointing the issue at hand.

I do not suggest taking it AutoZone (or the like) because their computer diagnostic is not detailed. I took it there for the heck of it (b/c the auto shop was closed down for the day) and they printed off about 8 different things it could be. And the one the tech at AutoZone suggested I do is the oxygen sensors – and the Denali has 4 of them @ about $99/each. Had I done that, I would have spent $400 and not fixed the problem.

And Firestone thinks highly of them selves apparently. They wanted to charge $180.00 just to plug in the computer and read a screen to tell me what wrong – that’s more than the dealership – yuck!

I wish you the best in solving this issue.

Posted on Jul 29, 2009


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