2003 Chevy Siverado wont start

I'm having problems with my truck not starting. I did an oil change a few hours ago and now the truck wont start. The truck started after I did the oil change and the "Battery Not Charging" message flashed on the digital display. I check the battery cables, fuses and other things to make sure I had all good connections. After checking everything out, I noticed my windows nor electric door locks wouldn't work and the truck still wouldn't start. I disconnected the battery and reconnected it and that solved the windows and door lock problem, but now the service air bag light, anti-thieft, and the park brake light is up on the dash. What would cause this to happen? If anyone knows please let me know. To make matters worse, I'm in England and I know what these mechanics are after $$$$$$$$$$$!! This vehicle only has 32000 mls. May I add another thing, the horn wont stop sounding so I had to disconnect the horn relay. Sinse the truck was shipped out of the U.S., no GM dealer in Enland will honor the warrenty.

How long did you leave the battery disconnected? I would let is sit long enough to allow for it to completely discharge all electrical components then reconnect it and see if it makes a difference.

How long did you leave the battery disconnected? I would let is sit long enough to allow for it to completely discharge all electrical components then reconnect it and see if it makes a difference.

I finally got the problem down to the passlock system. Has anyone every had any problems with this anti-theft system on any chevy autos?