Here is the document I followed:

https://xoutpost.com/pdf/Heated%20wheel%20retrofit.pdf

Ridiculously well documented and complete.

My family is stoked that the rear seats are heated too!

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2004 X5 4.4 Build 01/04 Alpine White on Schwarz Dakota Leather, Anthracite Headliner
Xtrons Android HU, SPORT PKG, COLD WEATHER PKG(W/REAR HEATED SEATS AND HEATED STEERING WHEEL), CONVENIENCE PKG, FACTORY HITCH