Component Description

Sentry Key Immobilizer Transponder:

TRANSPONDER KEY
The Sentry Key Immobilizer System (SKIS) uses a transponder chip that is integral to each ignition key to communicate with the Sentry Key Immobilizer Module (SKIM). Ignition keys are supplied with the vehicle when it is shipped from the factory The transponder chip is undermolded within the head of the key. This undermold is hidden beneath an overmolded rubber cap.

Each Sentry Key has a unique transponder identification code permanently programmed into it by the manufacturer. Likewise, the SKIM has a unique "Secret Key" code programmed into it by the manufacturer as well. When a Sentry Key is programmed into the memory of the SKIM, the SKIM stores the transponder identification code from the Sentry Key, and the Sentry Key learns the "Secret Key" code from the SKIM. Once the Sentry Key learns the "Secret Key" code of the SKIM, it is also permanently programmed into the transponder's memory Therefore, blank keys for the SKIS must be programmed by the SKIM in addition to being cut to match the mechanical coding of the ignition lock cylinder. Refer to Electrical, Vehicle Theft Security, Transponder Key, Standard Procedure - Transponder Programming.

The Sentry Key's transponder is within the range of the SKIM's transceiver antenna ring when it is inserted into the ignition lock cylinder. When the ignition switch is turned to the ON position, the SKIM communicates with the Sentry Key via a Radio Frequency (RF) signal. The SKIM determines if a valid key is present based on the information it receives from the Sentry Key. If a valid key is detected, that fact is communicated to the PCM via the PCI bus and the vehicle is allowed to continue running. If an invalid key is received by the PCM or no status at all is communicated, the vehicle will stall after two (2) seconds of running. The indicator light will be flashing at this point. The Sentry Key's transponder can not be repaired. If it is faulty or damaged, it must be replaced.

Common communication problems:
- Two transponder keys too close together.
- Speed Pass too close to transponder key.

Solid indicator that there is a system failure.
- Loss of PCM communication.
- Failed antenna circuit.

VTSS/SKIS INDICATOR LAMP
The Sentry Key Immobilizer System (SKIS) uses an indicator light to convey information on the status of the system to the customer. This light is shared with the Vehicle Theft Security System (VTSS). The light is located in the Message Center. The indicator light is controlled by the Body Control Module (BCM) based upon messages it receives from the Sentry Key Immobilizer Module (SKIM) on the PCI bus.

The BCM performs a four second bulb check, regardless of SKIM messages. After the bulb check, the lamp is controlled according to SKIM messages. Then, the SKIM sends messages to the BCM to operate the light based upon the results of the SKIS self tests. The light may be actuated in two possible ways, flashing or on solid. If the light comes ON and stays ON solid after a power-up test, this indicates that the SKIM has detected a system malfunction. If the SKIM detects an invalid key when the ignition switch is moved to the ON position, it sends a message on the PCI bus to the BCM, to flash the light. The SKIM can also send a message to flash the light and generate a single audible chime at the same time. These two events occurring simultaneously indicate that the SKIS has been placed into the "Customer Learn" mode. Refer to Electrical, Vehicle Theft Security Transponder Key, Standard Procedure - Transponder Programming for more information on the "Customer Learn" mode. If the light comes ON and stays ON after the power-up test, diagnosis of the SKIS should be performed using a DRB III scan tool and the appropriate Body Diagnostic Procedures manual. The light is not a serviceable component.