Vehicle Theft Deterrent (VTD) Circuit Description

PASS- KEY SYSTEM COMPONENTS
Ignition Key (Transponder)
The ignition key for PASS-Key III equipped vehicles is a typical ignition key with a transponder pellet located in the plastic end of the key. The ignition key transponder value is used to determine if a valid ignition key is being used to start the vehicle, there are approximately three trillion different transponder values available. This vehicle has two types of ignition keys.
^ Master key (black plastic end) which can start the vehicle and lock/unlock all door locks, all storage components and the rear compartment lid lock.
^ Valet key (gray plastic end) which can start the vehicle and unlock/lock all doors but can not unlock/lock the storage compartments, or rear compartment lid lock.

IMPORTANT: The transponder values are not readable and can not be serviced separately.

PASS-Key III Reader Exciter
The PASS-Key III Reader Exciter is part of the ignition lock cylinder. The following inputs/outputs are all supplied by the VTD module:
^ Battery voltage, circuit 1459 (BLK).
^ Sensor signal, circuit 1836 (YEL).
^ Sensor return, circuit 1835 (WHT).

PASS-Key III Theft Deterrent (VTD) Module
The VTD module contains the software for controlling the PASS-Key III system. The VTD module uses the following inputs and outputs to control the PASS-Key III system.

Inputs
^ Battery voltage from the underhood junction block IP fuse, circuit 440 (ORN).
^ Ignition start voltage from the ignition switch, circuit 1390 (WHT).
^ Ground, circuit 451 (BLK/WHT).

Outputs
^ Battery voltage to the PASS-Key III Reader Exciter, circuit 1459 (BLK).
^ Sensor signal to the PASS-Key III Reader Exciter, circuit 1836 (YEL).
^ Sensor return to the PASS-Key III Reader Exciter, circuit 1835 (WHT).
^ Starter relays, grounds circuit 625 (YEL/BLK).
^ Password exchange with the PCM (fuel enable), class 2 message.

Powertrain Control Module (PCM)
The PCM verifies that the passwords received from the VTD module via the class 2 serial data line are valid. If a password is invalid the PCM disables the fuel delivery system. If the password is valid the PCM enables the fuel delivery system.

Starter Relays
The starter relays are controlled by the VTD module via the starter enable control (CKT 625, YEL/BLK). If the VTD module measures the correct transponder value, the VTD module switches the starter enable control (CKT 625, YEL/BLK) to ground. The relay is energized if the ignition switch is in the START position and the gear selector is in the PARK or NEUTRAL positions.