Sentry Key Immobilizer System

The Sentry Key Immobilizer System (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 lock cylinder. See Figure . The SKIM uses RF signals to communicate with special Sentry Key transponder keys. See Figure . Each SKIM is programmed with a unique "Secret Key" code and security code. The SKIM sends the "Secret Key" code over the Programmable Communications 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 (up to 8 keys). The SKIM also stores the Vehicle Identification Number (VIN) in memory from PCM during initialization. See SENTRY KEY IMMOBILIZER MODULE INITIALIZATION PROCEDURE  under PROGRAMMING.

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

SKIM can also control operation of sun sensor/Vehicle Theft Security System (VTSS) Light Emitting Diode (LED) by sending messages to Body Control Module (BCM). BCM then controls LED.