Working on modern car electrics is something you have to be very careful with. As an auto electricians we thought we had seen most things electrical with cars.
This vehicle took us by surprise quite a bit. A customer was trying to fit a central door locking kit to a 2011 Volkswagen Polo. The customer mistook the central convenience module for a central locking module and cut it off the car.
After finding the car would not start we had a phone call to repair the wiring. Somebody else had looked at the car before it came to us and had attempted to solder the plugs from a later car into the loom. All was going well until they came across wires that were different colours.
So armed with pages and pages of wiring diagrams we started to put the loom back together. We had to trace the pin numbers and wiring colours and cross reference them to get the circuits connected back up to the right place. There was no room for error, one mistake could cause damage to the module and would mean it would need to be replaced. After hours of tracing wires we got everything connected back up and working as normal.