Car electronics

[LittleBit]

I thought I did understand electronics slightly but today I'm no longer sure...
In my car there is a light module with an ordinary lamp.
A diode (just a 1N4007) is mounted anti-parallel over the lamp.
Why is this done ?
(if you want to should "voltage spike protection" than Why is it mounted over the lamp and not over the voltage spike source like a relais ?)
Did you ever find it in your car ?

PS,
This question is based on the assumption that for some people their car is their home and so it is part of their domotica

[AshaiRey]

That way you can detect if the lightbulb is broken or not.

[LittleBit]

That way you can detect if the lightbulb is broken or not.

Interesting.....
so to do this test,
some electronic-device in the car should put a negative voltage on the line
to test the difference between
1) lightbulb broken
or
2) fuse broken
So if this is correct,
which device/unit/component is putting the negative voltage on the wire ?

PS
We should implement this in hour home systems also