Vehicle Theft Deterrert (VTD)

The personal automotive security system (PASS-Key) is standard equipment on the vehicle. The system is designed to prevent vehicle theft by disabling the engine unless an ignition key with a specific electrical resistance is used in the ignition cylinder.

There are 15 different ignition key resistance values. Of the 15 different resistance values, or key codes available, only one will work with each Body Control Module (BCM). Once the key code is programmed into the BCM, the code is stored in non-volatile memory.

The PASS-Key system prevents the engine from starting by controlling the theft deterrent relay and the Powertrain Control Module (PCM) fuel enable input. If the PCM does not sense the proper fuel enable signal, fuel will not be provided to the engine.

If the wrong resistance value is sensed when the ignition switch is in the ON position, the BCM will not ground the theft deterrent relay control circuit and will not provide the fuel enable signal for approximately three minutes. The engine is prevented from starting and discourages a thief from trying key codes or resistance values at random.

If the correct resistance value is sensed when the ignition switch is in the ON position, the BCM will ground the theft deterrent relay control circuit and enable fuel delivery. The engine will start normally.

If the PASS-Key system detects an open or short to ground when the ignition switch is in the ON position, the BCM will default to fail enable mode. Fail enable occurs when the proper key resistance is sensed before the open short to ground occurs.

Fail enable will illuminate the security indicator lamp and allow the operator to stop and start the vehicle until the problem is corrected. The PASS-Key system includes the following components:
^ Ignition key
^ Ignition cylinder
^ Body control module (BCM)
^ Theft deterrent relay
^ Powertrain control module (PCM)
^ SECURITY indicator

Ignition Key
The ignition key is a typical square ignition key blank with an imbedded resistor. The key blank and resistor are not serviceable separately. There are 15 different resistance values. The ignition key also has mechanical cuts similar to non-PASS-Key ignition keys.

Ignition Cylinder
The ignition cylinder contains a set of electrical contacts used to measure the resistor in the ignition key. When the ignition key is inserted into the lock cylinder, the resistor in the key makes contact with the electrical contacts inside the ignition cylinder.

Body Control Module
The Body Control Module (BCM) contains the theft deterrent system logic. The BCM reads the key code from the ignition cylinder when the ignition is turned to the START position. If the code is correct, the BCM will enable the theft deterrent relay and will send a fuel enable signal to the PCM via class 2.

If the BCM receives the wrong code, the BCM will immediately go into tamper mode. The tamper mode will lock-out the vehicle starter and fuel injectors for 3 minutes. The SECURITY indicator will flash while the BCM is in tamper mode.

Theft Deterrent relay
The theft deterrent relay is used to prevent the engine from cranking if the correct resistance is not sensed at the ignition key. It prevents the engine from cranking by opening the circuit to the starter solenoid.

Powertrain Control Module
The PCM communicates with the BCM over the Class 2 serial data line. When the BCM enters tamper mode, it sends a Class 2 serial data signal to the PCM in order to disable the fuel injection system. If the BCM receives the expected ignition code, the BCM sends a Class 2 serial data signal to the PCM in order to enable the fuel injection system. The PCM then allows the vehicle to start.

SECURITY indicator
The SECURITY indicator is located on the instrument cluster. The SECURITY indicator is controlled by a Class 2 serial data message from the BCM.