I don't know if it still applies but I remember reading of a BMW owner whose car needed a new battery. He bought one, disconnected the old one, fitted the new one and the car wouldn't start. He had to have it lifted to a BMW dealer who had to program in the new battery. Apparently if he had kept a constant 12v connected to the car's wiring, i.e. the car's battery cables, it would have been OK.
The first time I heard of microprocessors in vehicle wiring was when my neighbour was a professional MBenz mechanic. A van came in to the garage with a rear brake light out. He changed the bulb for a new one and it still didn't light. (this was before LEDs). He checked the bulb holder and there was no volts when the pedal was pressed. The fault was in the microprocessor in the light cluster which failed to connect the incoming 12v wire to the brake light bulb holder. A new light assembly was needed, and it had to be programmed into the body ECU. The same principle applied to his own private Transit which needed a new starter motor. He went and bought a motor from a scrap yard but it wouldn't turn the engine. He had to have it tow started, and drove it to a Ford dealer who said aha, you MUST have a NEW genuine Ford starter motor, you can't fit a used one. They were the only ones who could connect the vehicle to The Main Computer In Dagenham To Which All Fords Must Be Connected At All Times And In All Places. The dealer was then able to fit a new Ford starter motor and reprogram the engine ECU to accept the new starter motor.
I would have thought he could have run a cable from the battery through a switch to the starter solenoid, and by pass the flippin computer.
Reason number 2,349,238 why I won't have a new vehicle. Well, I might have a new electric bike , , , , but I probably wouldn't be able to lift it on to my bike rack.
