Check engine, traction control system, AWD and VSC (flashing) light are on.

Don't think anyone truelly knows solution. Have had and found every answered possible even fro very well known garages and car dealerships service department so far over 2 years had downstream oxygen sensor, upstream sensor, gas cap, wheel sensor, caytilic convertor, use better gas, don't drive far enough and u name it not to mention they used some 08 parts on cars partially though model year. Anyone really know or just more guesses.

WHAT ARE THE CODES?

Its been coded to death by multiple certified mechanics at multiple garages over 2 1/2 yrs all shows oxygen sensor, down stream uses a 2008 gm sensor upstream is a Toyota sensor. Car built in 4/08 so leftovers used from previous year. Other suggestions was gas cap it works as suppose to one click and its from gm new if u take off cap after gas fill up and then put back on and start car you can hear a small click from gas cap.