Seat Position Sensor

A seat position sensor is installed on the driver seat. The seat position sensor allows the RCM to detect when the seat is forward of a given point on the seat track. The seat position sensor consists of a Hall effect sensor attached to the seat frame and a target plate on the seat base. While the ignition is on, the RCM supplies the sensor with a power supply of 12 V nominal, and monitors the return voltage. When the seat frame moves forwards, the sensor moves over the target plate, which changes the reluctance of the sensor. The change of voltage is detected by the RCM and used as a switching point. The switching point is when the center of the sensor is 3 ± 4 mm (0.12 ± 0.16 in.) from the leading edge of the target plate.

When the driver seat is forward of the switching point, the RCM increases the time delay between firing the two stages of the inflator in the driver air bag. When the seat is rearward of the switching point, the RCM uses the normal time delay between firing the two stages.