won't start

my friend has a 92 model truck and the coil won't fire he's checked the wiring through out the truck and could not find any problems the weird thing is the coil has a 12volts going into it and 12v coming out from the ground i checked the coil with a ohm meter and it checked out ok and another thing thats weird is when you turn on the head lights and put them on bright the dash lights and radio goes out someone checked the codes and said the temp was running at -56 degrees could it be possible that the computer went bad any help would be greatful thanks

problem was the computer had the ecm rebuilt and everthing works fine now