security system

You can't do that. Check my answer to your other post. What happens when you turn the key? The instrument light and gauges are working? No click can be heard? Did you check the fuses? Do you know how to bypass the starting circuit and check the starter directly? The ignition switch is also a common problem on these, however without the correct diagnostics you will spend a bunch of money for unnecessary parts. Better to tow it to a BMW specialty shop or to the dealership. Zee