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 two. 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 ten 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:
^ If the transponder value is correct, the theft deterrent control module sends a class 2 message containing the module's enable password to the PCM.
^ If the transponder value is incorrect, the theft deterrent control module sends a class 2 message containing a disable password to the PCM.
^ 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), it sends a class 2 message containing a disable password to the PCM.