I have a 2000 Mercury Grand Marquis that has.

I have a 2000 Mercury Grand Marquis that has about 135,000 miles on it. 2 weeks ago I had the car at a relatives and the horn started going off for no reason at all. I took it for a test drive to see if it would stop and it wouldn't, the horn was going off while driving. I parked it and pulled the horn fuse and this did not resolve anything. The horn continued to sound off whenever it wanted. I proceeded to drive the car home. When I did smoke came up from where the steering column cover meets the dash. The smoke dissipated and I didn't see any more. I then drove the car to and from work (47 miles round trip) with no foreseeable problems. The next day I fired it up and drove to work and still nothing wrong. I parked the car and worked a 8 hr shift. Next, I walked out to warm my car up and the car fired up right away. When I went back after 10 minutes of warming up the car was dead. I had a buddy jump the vehicle at work and it again fired up but then cut back out after like 45 seconds of running. After that the security light flashes rapidly and car will not turn over. I now have a cooling fan that turns on whenever it wants to as long as the battery is connected, a horn that triggers itself, and I could hear the ABS system trying to kick in by itself. I have since replaced the radiator fan relay, the EEC relay, and just replaced the ignition switch. None of this has helped. Now I can’t hook up my OBD code reader. The reader says it can’t link to the PCM through the data link connector. I also noticed that the check engine light will not illuminate when the car is turned on. Further I took out the “brain” and the cooling fan still comes on by itself. I had a family friend check all fuses and relays and everything checks out good. To me it sounds like I have a problem with the "brain"/engine control computer or maybe a short somewhere. What suggestions do you have to fix this problem?