Bonnet switch
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2004 Land Rover Discovery, 2003 Land Rover Discovery, 2002 Land Rover Discovery, 2001 Land Rover Discovery, and 2000 Land Rover Discovery. However, it is still accessible from the selected car via links, so may be relevant.
The bonnet switch is powered from the BCU and is used as a logical input for operation of the security system. The switch is normally open with the bonnet closed, when the bonnet is opened the switch contacts close to complete a circuit to earth and signal the change in state to the BCU.