Sentry Key Immobilizer System (Skis)

The SKIS uses Radio Frequency (RF) signals that are transmitted and received by the Sentry Key Immobilizer Module (SKIM) though a plastic ring that surrounds the ignition lock cylinder. See Figure . The SKIM uses RF signals to communicate with special Sentry Key transponder keys. Each SKIM is programmed with a unique "Secret Key" code and security code. The SKIM sends the "Secret Key" code over the Programmable Communication Interface (PCI) bus line to the Powertrain Control Module (PCM). The PCM also stores the "Secret Key" code. The SKIM sends the "Secret Key" code to each Sentry Key transponder key (2-8 keys). The SKIM also stores the Vehicle Identification Number (VIN) in memory from PCM during initialization.

When ignition switch is turned to ON or START position, SKIM transmits an RF signal to energize the Sentry Key transponder. If SKIM receives valid "Secret Key" and transponder identification codes, the SKIM sends a "Valid Key" message to PCM. PCM will allow engine start and run operation. If an invalid ignition key is used, SKIM will send invalid signal to PCM, causing engine to start and run for 2 seconds, then stop. If vehicle is started with invalid keys 6 times in a row, vehicle will shutdown until correct key is used.