Q: Camshaft position sensor keep failing after i replace it. after 2 miles the check engine comes back on for that sensor 2003 BMW 745Li

Hello - you don’t mention the specific problem codes you are getting, but the problem you are having may not be the cam sensor itself. Rather, the problem could be the "v-shaped" timing chain guide between the cylinder banks. This engine is notorious for wear on this guide, which changes cam timing for Bank 2 (passenger side) of the engine, and causes a variety of cam timing problem codes. I recommend a loss of power inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, confirm this diagnosis, and give you an accurate assessment of damage and cost estimate for repairs.