2009 Pontiac G6 auto start wont work

I have a 2009 Pontiac G6 sedan. My auto start is
on in as I've checked multiple times. Check engine
light is on but the only code its throwing is an o2
sensor. I've tried hitting my lock button and then
the auto start button as directed, no lights flash at
all. My key fob is very slow, takes an excessively
long time to lock and unlock my car, I have to hold
the buttons down for a minute and even then I
have to try multiple times sometimes to get it to
work in general. At the same time my rear
passenger door on the drivers side tends not to
unlock at all, even when using the lock/unlock
button inside of my car. I have absolutely zero
knowledge of the ins and outs of anything really to
do with cars and etc. Can anyone please help
guide me in the direction of how to get my auto
start to work?