This could be handy on an X5 (inside illuminated door handle). My car is a 2002 (pre-face-lift) with basic options (which I've been upgrading).

I found the part numbers - you can do this for front & rear doors (all depends on your budget).

51.41.7.000.231 (left front)
51.41.7.000.232 (right front)

51.42.7.000.233 (left rear)
51.42.7.000.234 (right rear)

63.31.6.907.750 (LED)

The LED is apparently in nearly all E53 (pre & post facelight) cars and just taped over in the door harness. I need to check my car, but it's raining right now.

For those who have done this - you indeed simply found the electric connector (and the LED?) inside the door harness?

Might you have the part number of the socket (in the event a pre-facelift car doesn't have this installed)?

For those who have this option (or have retrofit) - I assume they light up with the dash & parking lights, correct?

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2002 Euro X5 (E53) 3.0 diesel (M57)
5 speed manual with UUC short shifter.
Pre-xDrive NV125 transfer case (chain & gears).
Factory Xenon headlights, Spyder LED tail lights
Updated vortex crankcase breather.
Motorsport dead pedal, factory fire extinguisher, factory first aid kit, factory F&R mud flaps, factory PDC

Bilstein B6 shocks F&R
Redline oil has replaced "lifetime" fluids (F&R diff, manual transmission, transfer case and P/S).
Dimple magnetic drain plugs in all compartments.