2003 Pontiac Aztek Electrical Issues

Hello, looking for some help. It started about a week ago when I went to start the car the Security light on the dash came on and the car did not turn over. I removed the battery for about 5 minutes and then it started but it would not going in gear. Did the same again and it started and got it in gear and drove home. Shut it off and tried to restart it did but Security light came on and didn't go into gear. The next morning I started it and drove off no issues, on the way to work the brake light came on and buzzer dinged and the dash gauges all went dead but came back on shortly. I have been driving this for approx. One week like this with diffrent things going on each time, don't have the time or room to list them all. I put my scanner (PC stlye with software) on it and with the door open it will not communicate with the PCM, close the door and then it links. Cleaned the battery terminals, checked the connections to the PCM and the BCM and all look fine. I have not gone through the ground circuit, that is next. Do you have any ideas as to what this is? Sounds like the BCM to me but none of the dealers seem to know what they are doing or they just don't want to help. Thank you for your time and any help would be great, all of my schematic info is coming from AllData, again thanks.
Rob