Just recently I noticed my check engine light has come on and I'm getting error codes P0171, P0106, P015B, and P1101. Only problems I've noticed are when stopped at a light or stop sign there is some shaking going on but other than that everything has seemed fine. Any ideas what the problem could be? I'm unfortunately past my powertrain warranty of course. I'm a complete novice when it comes to cars so should I still take it in to my Chevy dealer or just take it to a mechanic? Thanks ahead of time for the help.