[alufers]

A car lamp will usually have a few different bulbs/LEDs (daylight running lights, headlights, high beam, indicators also the height adjustment motor), so it's less wiring to run a CAN pair and constant +12V to the fixture, than to wire each light type individually.

I think the light can also report a failed lightbulb to the dashboard.

[moffkalast]

There are afaik already multiple CAN busses in your average car with different data rates, might as well have a separate one for all the risky stuff that's easily accessed? This is some basic security shit.

[trollied]

Some are even more complicated. My car has lights that will track the road going round corners etc. I imagine there are other inputs it requires elsewhere in the car (cameras etc).

[jacquesm]

My car had that in ... 1987 ... and it was a 13 year old car at the time.

[is_true]

it tracks the road or the position of the steering wheel?

[oh_sigh]

A problem with the CAN bus is that there is no way to tell what node sends what message on the bus, so you can't have something like a filter that only processes headlight-related messages coming from headlights. I guess you could actually do it, but it would require every node being able to sign their messages, which would add a lot of cost.