It's a good question, however E53 don't have automatic seat heating. It's activated by the switch strip just in front of your front ashtray. Switches are at the extreme left and extreme right.

Italian market E53, I have one originally with cloth mechanical seats. I retrofit heated leather sport seats up front, leather rear (no heat) and the matching door cards. Fairly easy to do, I did a write-up on this ~4 years ago.

Someone might have retrofit a basic panel in the seat, have you checked?

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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.