I have a 2012 Acadia with 169K miles. 6 months ago I replaced all O2 sensors. After doing so I continued to get a lot of O2 codes, check engine light and running rough. The company I bought the O2 sensors from sent me 2 new heated ones under warrenty as I thought they were the problem. After reaplacing them I now get P0030 code and vehicle still runs rough especialy since it is cold outside. Any suggestion as where to start looking for this heat circuit problem? Just seems like it is like looking for a needle in a haystack.