WARNING: This page is about a different car, the 2003 BMW X5, 2002 BMW X5, 2001 BMW X5, and 2000 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
Install special tool 13 3 063 and special tool 13 3 061 (pressure gauge).
Start engine and check engine oil pressure.
Specified value.
Fig 1: Checking Engine Oil Pressure With Pressure Gauge