2004 S80 suddenly died and won't turnover
 

Hi, my interior lights are out, the door chime is out, the remote door lock won't work. When I turn the key, nothing. Headlights are on and bright but high beam lever does nothing. Headlights don't dim or change at all when trying to start it. First time this happened, the e.c.m. under the dash above the pedals had a loose plug somehow. When the mechanic touched it, everything worked again. Thoughts on what it could be? Thanks all!