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compression on the cylinder. I have since learned that the AFM does have something to do with it. I have a service bulletin in hand that says other wise!! so long story short if you own a GM 06-09 with AFM you are going to have trouble with it! I own 4 GM products and my parents own 3. at this time I have two up for sale driving one till I can get Sierra fixed and then both of those are going up for sale!! After all this I will never own a GM product again!0 ·October 2014
lawbob I was reading your post. I hope that this solves your problem with your Sierra. I have had on going problems with my 2009 Sierra as well. At 73k miles the dealership pretty much had to rebuild the top end of the motor on my truck. New rings, bearing kit, heads were reworked and valve seals replaced. Fast forward to a month ago. Truck started having a bad miss in #6 cylinder plug was fouled out from oil. I have a employ that works for me that is a 30 year retired GM service tech. we performed a compression test on the #1 cylinder to compare to the #6 cylinder more than 80 psi difference between the two. My truck now has 123K on it and is out of warranty so I call GM to see if there is any help from them on this. service tech had me to take it to a dealership to run test on it. After having my truck for a week they call and tell me that the AFM is out on it and it is going to run 3K to fix the problem. I thought this was bs because the AFM wouldn't have anything to do with the com0 ·October 2014