Hope im posting this in the right place, im a newbie on here..So my issue:

One night went to car late at night to get something from trunk. When I closed trunk alarm went off, but was a steady constant Horn honking as opposed to a pulsating honk the alarm would do. Put key in car and turn to accessory to stop honking. When removed keys and shut door and locked, the horn came back on. Seemed like every little thing was setting it off. Took fuse out for horn. Car would start but absolutely no acceleration at all when stepped on gas, and noticed that TCS OFF and Swerve light was on. When I disconnected battery and reconnected I started car, and then the lights were off and car accelerated fine. Until next time I parked then it started over, then had to disconnect/reconnect..The other odd issue that started with this is that when I turn on turn signals, the hazards come on?! Check engine light alaways comes back on after being cleared constantly and says "U0100" - Lost Communication With ECM/PCM

What on earth could this be?

My car has 164000 miles. My car has an automatic transmission.