The brief
This X5 came in after a freelancer had fitted an in-car camera, and the install had gone badly wrong. Tapping into the wrong wires had shorted the electrical system, and the damage had reached two important control modules, the junction box electronics that runs the body electrics, and the engine control module's circuit board. Modern BMWs run their electrics through a network of control modules, and they don't take kindly to power being fed where it shouldn't be. A short in the wrong place can fry a module's internals in an instant, and once a module is damaged the car can refuse to start, throw a cascade of fault codes, or lose whole systems at once. Damaged modules don't recover, so the fix is to replace them, code the new ones to the car, and put the wiring back the way it should be.
The diagnosis
Diagnostics showed a spread of fault codes pointing at the body control electronics and the engine control module, both damaged by the short from the camera wiring, which is why the car was dead. The wiring around the install was a mess, tapped and spliced in the wrong places. That's a replacement of the damaged modules, coding them to this car, and a proper job on the wiring, rather than trying to revive electronics that had been shorted.
The work
The damaged junction box electronics and the engine control module circuit board were replaced with the correct genuine BMW units, each coded and programmed to this car so the network recognises them. The botched camera wiring was removed, and any accessory wiring put back the right way, fused and tapped from the proper points so it can't short the system again. The fault codes were cleared and every module checked talking to the rest. A road test confirmed the X5 starting and running normally, every system working, and no fault codes.
The outcome
The X5 starting first time, running normally, every electrical system working, no fault codes, and the wiring done properly. The car went home alive and well. Cheap, careless wiring is what got it into this state, so replacing the damaged modules, coding them in, and doing the wiring the right way put it back to standard, which is the only safe way to leave a car's electrics.