How to retrofit B pillar ambient light to the BMW F30/31

It's pretty much straight forward.

You need to unplug 2 wires (brown and grey-red) from the car and plug them to the B pillar connector, and add 2 wires (brown and orange) to the car from retrofit kit.
(3 wires if you have light package )

Retrofit kit has 3 wires:

Brown (power)
Orange (orange light)
Blue (blue light)

B pillar retrofit kit: https://www.aliexpress.com/item/B-pil...

Clips for wireing harness: 61 13 6 964 200

NOTE:
If your car does not have light package, you won't be able to connect blue light (blue wire), you will only have orange light.
This means that you also won't be able to control B pillar light from iDrive.
You can only control brightness from headlights switch. (Ambient light controller