Antitheft and Alarm Systems: Description and Operation

GENERAL DESCRIPTION
The vehicle theft alarm (VTA) is a logic-controlled system. It monitors the vehicle doors, hood, trunk or liftgate, key cylinder, and ignition for unauthorized operation.

The system has the following components:
^ Vehicle Theft Alarm Module
^ two door ajar switches
^ hood ajar switch and striker
^ trunk key cylinder sensing switch
^ two door key cylinder disarming switches
^ instrument panel set lamp
^ engine controller
^ horn and horn relay
^ park and tail lamps
^ power door lock circuits
^ ignition switch.

FUNCTIONAL OPERATION
When something triggers the alarm, the system will signal for about 18 minutes. For the first three minutes the horn will sound. Then the park and turn signal lights will flash for another 15 minutes.

Tamper Alert - If the horn sounds three times when either front door is unlocked, the alarm was activated. Check the vehicle for tampering.

Manual Override - The system will not arm if the doors are locked using the key or the manual lock control.

When an unauthorized entry into the vehicle occurs, the VTA module sends a message via the CCD bus to the engine controller that it is not OK to start the engine. The engine controller then zeroes out the pulse width to the fuel injectors after the engine has been started, thus shutting down the engine (start and stall condition).

The engine will not start until the system is disarmed.

The VTA module has the capability of providing bias on the CCD bus when the body controller is powered down.

To avoid both an audible alarm and the engine kill feature causing a problem in the assembly plant, an initialization procedure is included in the VTA system. This procedure requires that the vehicle has recorded 20 engine cranks. Therefore, the VTA system will be functional on all vehicles and will require dealer verification.

To verify the system, proceed as follows:
^ Open the driver's door.
^ Remove the ignition key (but keep it in hand).
^ Lock the doors with the power lock switch.
^ Close the driver's door.
^ If the instrument panel theft alarm "SET" lamp flashed, the system is operational and verified. If not, 20 engine cranks have not occurred, or there is a problem with the theft alarm system.