2008 Avalanche LTZ, 89,500 miles.
Just got Stabiltrak off and service traction. This is the third time since June 2013.

Vehicle repaired by Chevy dealer in Kalispell, Montana in June 2013.
Service stabilitrac, replace valve cover,replace all spark plugs and wires, clean injectors. With oil change over $900
Vehicle repaired by Dealer in Puyallup, WA in Aug 2015. Same symptoms.
Replaced all spark plugs, replaced left valve cover gasket . (over $900)

What codes were they getting that caused them to take the actions that were taken?

Are you also getting the reduced power indication as well?

Are there any powertrain codes stored?

No codes other than it all of a sudden is riding rough. Same symptoms as June 2013 and Aug 2015. I am attempting to take it to the dealer who "fix'ed" the vehicle in 2013. (I purchased the vehicle from this dealer). In 2015, I was in Puyallup Washington and had to take it to that dealer prior to traveling back to Montana. Same symptoms, rough riding, stabilitrak, service traction. And the vehicle seems to always be a quart low in oil.

You make it look like it is a stabilitrak problem, when it is another problem that is causing it and the traction control to be turned off...

We would need the specific codes that should be written on the repair order....

Just looked at work orders. The dealer in 2013 did not put any codes. The dealer in 2015 did indicate code P0300

Whenever you have a "misfire", this can cause the vehicle to shut down other systems, like stabilitrak and traction control......and if those lights came on, they should have created "C" codes, which probably would have confirmed that they were shut down, not that they had a problem....

Your problem seems to be a misfire, and there are MANY TSB'* on the problem........I was wondering why valve covers were being removed, and it was because they were looking for a possible drive train problem....

Apparently, they were trying everything on the first fix, so the question is, which fix actually fixed it? The second time, it was just the plugs......

A scan tool will tell you which cylinder has the most misfires.....a good tech would have noted this on each repair order.....to see plugs having to be replaced this often, seems to indicate fouling in the cylinders......

Thanks for the info. Sometimes I think the dealers (service) are not willing to acknowledge that this is an ongoing problem throughout the GM world.