[PoshBreeze]

I don't believe what you are describing is necessary. I am pretty sure you could have a module where the switches are wired normally into something and that communicates with the main bus. I am pretty sure this is how a lot of cars already work from watching people work on more modern vehicles.

In any event. I've never heard a good explanation of why I need all of this to turn the lights on or off in a car, when much simpler systems worked perfectly fine.

[sokoloff]

Many of the low-speed switches are connected to a single controller that then interfaces over LIN or CAN to the car.

Reducing the copper content of cars and reducing the size of the wiring bundles that have to pass through grommets to doors, in body channels, etc. was the main driver. Offering greater interconnectedness and (eventually) reliability was a nice side effect.

It used to be a pain in the ass to get the parking lights to flash some kind of feedback for remote locking, remote start, etc. Now, it’s two signals on the CAN bus.

[PoshBreeze]

OK, thanks for the explanation.

> Offering greater interconnected news and (eventually) reliability was a nice side effect.

I am not sure about that. You still suffer from electronic problems due to corrosion around the plugs, duff sockets and dodgy earths as the vehicle ages.