SRX 2WD V8-4.6L VIN A (2004)
Alarm Module: Description and Operation
THEFT DETERRENT CONTROL MODULE
Vehicles with steering column mounted ignition switches have the exciter integral with the theft deterrent control module which is located within the
steering column. Vehicles with instrument panel mounted ignition switches have exciter modules separate from the theft deterrent control module with
the vehicle wiring harness connecting the 2. The theft deterrent control module for vehicles with instrument panel mounted ignition switches is located
within the instrument panel. The theft deterrent control module can learn up to 10 keys (transponder values).
The theft deterrent control module uses the following inputs, battery voltage, ignition switched voltage and ground circuit. The theft deterrent control
module uses the following outputs, password exchange with the PCM (fuel enable/disable) via class 2 serial data circuit.
When an ignition key is inserted into the ignition lock cylinder, the transponder embedded in the head of the key is energized by the exciter coils
surrounding the ignition lock cylinder. The energized transponder transmits a signal that contains its value, which is received by the theft deterrent
control module. The theft deterrent control module then compares this value to a value stored in memory and performs one of the following functions:
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If both the transponder value and the calculation to the challenge are correct, the theft deterrent control module will send the fuel continue
password to the ECM via the serial data circuit.
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If either the transponders unique value or the calculation to the challenge is incorrect the theft deterrent control module will send the fuel disable
password to the ECM via the serial data circuit.
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If the theft deterrent control module is unable to measure the ignition key transponder value for one second due to a damaged or missing pellet or
a damaged exciter, the theft deterrent control module will send the fuel disable password to the ECM via the serial data circuit.
IMPORTANT: On some vehicles, if the VTD system is unable to read the ignition key transponder value after the vehicle has started, the VTD
system will consider itself malfunctioning. The VTD system will enter a fail enable state and will command the security indicator to illuminate. When
the VTD system is in a fail enable state the vehicle will NOT stall or stop running. If the VTD system is in a fail enable state when the ignition is
switched OFF, the VTD system will remain fail enable until it is able to read a learned ignition key transponder value. When the VTD system is in a
fail enable state the VTD system is NOT active and the vehicle will start. This feature is NOT available on all GM vehicle lines.
