any resistance in the bus lines can cause comunication errors. the bus lines cannot be repaired either. if there is a broken line and you solder it back together, you effectively shorten that line and the messages sent between the two wires are no longer in sync. the resistance could be caused by corrosion in the wire caused by chaffed insulation allowing water to get into the wire. it could be shorted directly to ground somewhere, theres quite a few ways it could happen but if the bus lines are the problem you have to buy a whole harness. it's not likely the bus lines are the problem but i'd definately check them before i replaced control modules.