BMW Repair Questions? Ask a Mechanic for Answers ASAP
I suspect the Alarm Sensor for the bonnet is the same one that tells you when if the bonnet is open. I would think it will be part of the bonnet catch assembley. Look at the bonnet catch and you will probably see a Wiring Harness going to it as well as the release cable.
I don't think disconnecting it will acheive anything because it will see it as Open Circuit and as such register that the bonnet is open.
The best way forward is a Full Diagnostic Code Read to establish what code(s) if any are present and then a check through Live Data of all of the door switches to check their operation.
If a door switch is found to not be working through Live Data a check of the Wiring Harness would then also be necessary. A continuity check from the sensor to the module to eliminate the wiring and a continuity check of the switch to eliminate t he switch. Rectify as necessary depending on results.