You can use the "unlock and lock" function of the diamond key...but not to start your vehicle.

To program the FOB function is pretty easy. Search YT for a video--as there are many. For free, btw.

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2003 BMW X5 3.0i -- MT5, 3.64s final gears, H&R lowering springs, K-Mac bushing kit
2007 BMW X3 3.0Si -- MT6