1999 Seville Electrical problem
 

My 1999 Seville SLS seems to have electrical problems. The dash get bright and hoes dim, service air bag comes on, speed limited to 90, the gas gage goes to E, the windows, doorlocks mirrors, radio stop wroking. It even effects the transmission, it will not go into first gear. I f you turn the car off all the items work window raidio etc. What coule be causing this, coule it be the BCM. .Could this be swappeed from a used sls or does this have to be programmed.