Keyless Entry: Description and Operation

SENTRY KEY IMMOBILIZER SYSTEM
The Sentry Key Immobilizer System (SKIS) is available as a factory-installed option on this vehicle. Vehicles equipped with the Vehicle Theft Alarm (VTA) are also equipped with SKIS. The SKIS provides passive vehicle protection by preventing the engine from operating unless a valid electronically encoded key is detected in the ignition lock cylinder. The SKIS used in combination with the export premium version of the VTA adds a steering shaft lock feature that provides passive protection by preventing the vehicle from being steered unless a valid electronically encoded key is detected in the ignition lock cylinder, but is only available in vehicles manufactured for sale in certain markets where it is required equipment.

The SKIS includes the following major components, which are described in further detail:
- Sentry Key Remote Entry Module (5) - The Sentry Key REmote Entry Module (SKREEM) is sometimes referred to as the Wireless Control Module (WCM). The SKREEM is located on the instrument panel to the right side of the steering column near the ignition lock cylinder housing and an integral molded plastic antenna ring circles the ignition lock cylinder like a halo. The SKREEM and its antenna are concealed beneath an ignition switch bezel on the instrument panel.
- Sentry Key Transponder - The Sentry Key transponder is contained within the Remote Keyless Entry (RKE) transmitter integral to the head of the ignition key.
- Security Indicator (4) - A security indicator is integral to the Electromechanical Instrument Cluster (EMIC).
- Shaft Lock Module (3) - A shaft lock module is located in a bracket integral to the lower end of the steering column casting below the instrument panel in the passenger compartment of vehicles built for sale in certain export markets where it is required equipment.

The Sentry Key Immobilizer System (SKIS) is designed to provide passive protection against unauthorized vehicle use by disabling the engine after about two seconds of running, whenever any method other than a valid Sentry Key is used to start the vehicle. The SKIS is considered a passive protection system because it is always active when the ignition system is energized and does not require any customer intervention. The SKIS uses Radio Frequency (RF) communication to obtain confirmation that the key in the ignition switch is a valid key for operating the vehicle. The microprocessor-based SKIS hardware and software also uses electronic messages to communicate with other electronic modules in the vehicle over the Controller Area Network (CAN) data bus.

Pre-programmed Sentry Key transponders are provided with the vehicle from the factory. Each Sentry Key REmote Entry Module (SKREEM) will recognize a maximum of eight Sentry Keys. If the customer would like additional keys other than those provided with the vehicle, they may be purchased from any authorized dealer. These additional keys must be programmed to the SKREEM in the vehicle in order for the system to recognize them as valid keys. This can be done by the dealer using a scan tool or, if Customer Learn programming is an available SKIS feature in the market where the vehicle was purchased, the customer can program the additional keys, as long as at least two valid Sentry Keys are already available.

In vehicles equipped with an export premium version of the VTA, the SKIS also controls an electronic shaft lock module on the steering column that locks the steering shaft from rotation unless a valid key is detected in the ignition lock cylinder. The SKREEM communicates with the shaft lock module over a dedicated serial bus to monitor and control the shaft lock function.

The SKREEM performs a self-test of the SKIS and the shaft lock module each time the ignition switch is turned to the ON position, and will store fault information in the form of a Diagnostic Trouble Code (DTC) if a system malfunction is detected. The SKREEM will also send an electronic message to the instrument cluster if a fault is detected, and the instrument cluster illuminates the security indicator or displays a textual shaft lock error message in the Electronic Vehicle Information Center (EVIC) as appropriate. The SKIS can be diagnosed, and any stored DTC can be retrieved using a diagnostic scan tool.