Flickering lights and other problems

Let me start off by saying wwwooooooowwww to the new main page. I haven't been on bimmerfest in fooreeevver. I like the new look. So I guess I'll start. I have done the pedal trick and check the code online and it said it was the battery voltage. I will Recheck what I get and post that code. Ok so I'll get my lights flickering both inside and out. I also get my ac to cut on and off or the defroster for the rear windshield will also go on and off. When I have the headlights on and I put my left turn signal on it blinks really fast as if one of the bulbs are burnt(both are fine). When the headlights are off the turn signal blinks normally. Another thing I've noticed is that when I have a flickering light moment the check engine light will go on at the same time. Another problem I have face is that my lights (inside) will come on when I stop sometimes. So far I have had suggestions to check ground which I will try to do. If there's anything else you know of that I should check please tell me :thumbup:
Also if there's any tips on where I should start or links to check the ground I would appreciate it Thanks again Guys