BMW Questions? Ask a BMW Repair Expert for Answers.
I think I can help you. However INPA and ediabas software isnt going to help you with a k-can issue. First thing you will need to do is get to a connector with the bus connection and check for a cross short from high to low (with the battery disconnected) and then check for a short to ground and to power once you have isolated that you will need to start unplugging modules to see which one is causing the short if it isnt a mosule you will need to start shaking the wiring to find the chafed wiring I would start with where the accident repair was.
I cannot think of any K-Can wires near the front bumper, There are several K-Cans and modules attached to them you will need a wiring diagram for your vehicle and component location for it. The easiest module you can get to is the one I would start the testing on.
As for the battery replacement you will need to register the new battery in the vehicle not initialize it. It will work without registering it this just changes the way it charges the new battery.