If the "Alarm Fault" communication is displayed on the Message Center, the most possible cause is failure of the ultrasonic sensor module mounted on the headliner. This device monitors the inner of the automobile for intruders when the automobile is in the "superlocked" state. Alternate of the sensor is easy and, if you are lucky, will solve the problem. A Scientific Repair dispatch was issued on the subject, stating the problem is most commonly found on 1998 models. After this is a better version of the sensor was issued.

The most basic part in a car alarm method is the access alarm. When you open the front hood, trunk or any door on a fully protected car, the head triggers the alarm scheme. Mainly automobile alarm systems use the switching mechanism that is already built into the doors. Here recent cars, opening a door or trunk turns on the inside lights. The button that makes this work is like the system that controls the light in your refrigerator.

All you have to do to set up door sensors is add a new element to this pre-wired circuit. With the new wires in place, opening the door sends an electrical current to the brain in addition to the inside lights. When this current flows, it causes the mind to sound the alarm.

As an overall caring measure, new alarm systems naturally monitor the voltage in the car's entire electrical circuit. If there is a drop in power in this circuit, the brain knows that someone has interfered with the electrical system. Turning on a light, messing with electrical wires under the hood or removing an attached trailer with an electrical link would all cause such a drop in voltage.

Door sensors are extremely effective, but they offer rather limited safety. There are other ways to get into the car, and thieves don't actually need to break into your car to steal it from you. In the next pair of sections, we'll look at some of the higher car alarm systems that protect against craftier criminals.

TWO TYPES OF ULTRASONIC MOTION SENSORS:

 

ACTIVE ULTRASONIC MOTION SENSORS:

These type of motion sensors emit sound waves from transducers. When there exists some movement in the sound waves the waves get moved towards the systems receiver. In common sound waves creates detection over a complete field which weakens with distance and it is detectable over a distance of forty feet.

PASSIVE ULTRASONIC MOTION SENSORS:

These type of motion sensors usually use principle of sound. These type of sensors are similar to active sensors in producing waves. Most of them use these type of sensors in high range for increasing sensitivity.  

 

DISADVANTAGES:

• Some motion detectors may also provide false alarms when some objects  cross through them.
• Some vibrations and movement of wind may also cause false alarms.
• If a thief moves very slowly it cannot detect his/her movements.
• Full detection in larger areas with bigger objects is not possible using the passive systems.
• Also, objects like furnitures obfuscate sounds that is not detectable using the sensors.