Theft Deterrent Control Module
Vehicles with steering column mounted ignition switches have an exciter integral with theft deterrent control module that is located within steering column. Vehicles with instrument panel mounted ignition switches have exciter modules separate from theft deterrent control module. 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 10 transponder values. Theft deterrent control module uses battery voltage, ignition switched voltage and ground circuit as inputs. Theft deterrent control module uses password exchange with PCM (fuel enable/disable) through 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 the 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 message containing a disable password to PCM.