I have a 2014 LS with 1.8 and 31k miles, keep getting P171 code, have changed lower O2, sea foamed throttle body and sea foamed gas tank, put premium in the tank CEL goes out for a day and comes back on the next day. usually in the mornings the first stop sign I come to my engine stalls, or as I am pulling into my parking spot coming home at the end of the day. Also get message to service stabilitrak and traction control. took it to the dealer and they wanted to charge me $800 to change the o2 sensor and clean the fuel system. I have a cruze for a reason, I don't have $800 lying around. I change the oil every 5k. i have checked from other posts about the PCV valve and i dont feel any air from it. on a positive note after I sea foamed the throttle body my gas mileage went up significantly. I was getting decent gas mileage before.