Liberty Sport 2WD L4-2.4L VIN 1 (2002)
Alarm System Transponder: Description and Operation
Sentry Key Immobilizer Transponder
TRANSPONDER KEY
Each ignition key used in the Sentry Key Immobilizer System (SKIS) has an integral transponder chip. Ignition keys with this feature can be
readily identified by a gray rubber cap molded onto the head of the key, while conventional ignition keys have a black molded rubber cap. The
transponder chip is concealed beneath the molded rubber cap, where it is molded within a plastic mount into the head of the metal key In addition
to being cut to match the mechanical coding of the ignition lock cylinder, each new Sentry Key has a unique transponder identification code
permanently programmed into it by the manufacturer. The Sentry Key transponder cannot be adjusted or repaired. If faulty or damaged, the entire
key must be replaced.
When the ignition switch is turned to the ON position, the Sentry Key Immobilizer Module (SKIM) communicates through its antenna with the
Sentry Key transponder using a Radio Frequency (RF) signal. The SKIM then listens for a RF response from the transponder through the same
antenna. The Sentry Key transponder chip is within the range of the SKIM transceiver antenna ring when it is inserted into the ignition lock
cylinder. The SKIM determines whether a valid key is present in the ignition lock cylinder based upon the response from the transponder. If a
valid key is detected, that fact is communicated by the SKIM to the Powertrain Control Module (PCM) over the Programmable Communications
Interface (PCI) data bus, and the PCM allows the engine to continue running. If the PCM receives an invalid key message, or receives no message
from the SKIM over the PCI data bus, the engine will be disabled after about two seconds of operation. The ElectroMechanical Instrument Cluster
(EMIC) will also respond to the invalid key message on the PCI data bus by flashing the SKIS indicator ON and OFF.
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. 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 permanently stored in the memory of the transponder. Therefore, once a Sentry Key has been
programmed to a particular vehicle, it cannot be used on any other vehicle. (Refer to VEHICLE THEFT SECURITY - STANDARD
PROCEDURE - TRANSPONDER PROGRAMMING).
The SKIS performs a self-test each time the ignition switch is turned to the ON position, and will store key-related fault information in the form of
Diagnostic Trouble Codes (DTC's) in SKIM memory if a Sentry Key transponder problem is detected. The Sentry Key transponder chip can be
diagnosed, and any stored DTC's can be retrieved using a DRBIII scan tool. Refer to the appropriate diagnostic information.
