Theft Deterrent Control Module

Vehicles with steering column mounted ignition switches have exciter integral with theft deterrent control module which is located within steering column trim panels. Vehicles with instrument panel mounted ignition switches have exciter modules separate from theft deterrent control module with vehicle wiring harness connecting the two. Theft deterrent control module for vehicles with instrument panel mounted ignition switches is located within instrument panel. Theft deterrent control module can learn up to ten ignition key transponder values.

Theft deterrent control module uses following inputs, battery voltage, ignition switched voltage and ground circuit. Theft deterrent control module uses following outputs, password exchange with PCM (fuel enable/disable) via class 2 serial data circuit.

When an ignition key is inserted into ignition lock cylinder, transponder embedded in head of key is energized by exciter coils surrounding ignition lock cylinder. Energized transponder transmits a signal that contains its value, which is received by theft deterrent control module. Theft deterrent control module then compares this value to a value stored in memory and performs one of following functions:

• If transponder value is correct, theft deterrent control module sends a class 2 message containing module's enable password to PCM.
• If transponder value is incorrect, theft deterrent control module sends a class 2 message containing a disable password to PCM.
• If theft deterrent control module is unable to measure ignition key transponder value for one second (due to a damaged or missing pellet or a damaged exciter), it sends a class 2 serial data message containing a disable password to PCM.