G Sensor (4WD Models Only)
WARNING: This page is about a different car, the 2002 Nissan Pathfinder. However, it is still accessible from the selected car via links, so may be relevant.
The G sensor senses deceleration during braking to determine whether the vehicle is being driven on a high traction road (asphalt road, etc.) or a limited traction road (snow-covered road, etc.). It then sends a signal to the ABS control unit.
The reed switch turns on when it is affected by a magnetic field. During sudden deceleration (braking on a high traction road), the weight moves and the magnet in the weight moves away from the reed switch. The magnetic field then diminishes and the reed switch turns off.