Interior Sensor UIS (After 99 MY)
Similar to the FIS, the UIS monitors the vehicle interior for motion. The UIS uses ultrasonic sound waves instead of microwaves (less susceptible to magnetic interference). The UIS is a combined transmitter and receiver.
The interior sensor is mounted in the center of the headliner panel. Due to the design of the vehicles interior, the sensor is uni-directional and must be installed in the proper direction to ensure proper operation of the system (trim cover ensures directional installation).
Every time the DWA system is armed (signal STDWA), the sensor adapts to what ever objects might be stationary in the interior. The sensor emits ultra sonic waves in a programmed timed cycle. It receives echoes of the emitted waves.
The UIS amplifies the received sound wave signals and compares them with the transmitted waves. The UIS also checks the incoming echoes for background hiss (wind noise through a partially open window) and adapts for this.
- If the echoes are consistently similar, no movement is detected.
- If the echoes are altered, (inconsistent), the UIS determines motion in the interior compartment.
If motion is detected, the UIS changes to a constant cycle and the echo is compared again. If the inconsistency is still present the UIS sends the activate siren signal (INRS) to the GM.
The UIS is switched OFF when the vehicle is locked two times within ten seconds. The LED will flash one time for confirmation. This allows the sensor to be switched OFF to avoid false alarms when the windows are left open for venting.