My son has a 2012 Cruze that was throwing 171 and 1101 code. Valve cover fixed the 171 code and we finally took it to dealer after cleaning map, maf, and throttle body and replacing air filter. They came back and said it was the PCV tube from intake to turbo. So we ordered it and got it installed and it fixed the code but, now rpm fluctuates from 500 to 900 at idle and while stopped in gear and neutral also. It drives fine down the highway but at stop lights and while parked rpms fluctuate. I've sprayed around with carb cleaner and can't find any vaccum leaks. We put old PCV tube back on and fixed idle issue but now we're back to throwing 1101 code. Thanks for any help!