TRANSPONDER KEY
DESCRIPTION
Each ignition key (2) used in the Sentry Key Immobi-
lizer System (SKIS) has a transponder chip included
on the circuit board (4) beneath the cover (1) of the
integral Remote Keyless Entry (RKE) transmitter (3).
In addition to having to be cut to match the mechani-
cal coding of the ignition lock cylinder and pro-
grammed for operation of the RKE system, each new
Sentry Key has a unique transponder identification
code that is permanently programmed into it by the
manufacturer, and which must be programmed into
the Sentry Key REmote Entry Module (SKREEM) to
be recognized by the SKIS as a valid key. The Sentry
Key transponder cannot be adjusted or repaired. If
faulty or damaged, the entire key and RKE transmitter
unit must be replaced.
OPERATION
When the ignition switch is turned to the On position, the Sentry Key REmote Entry Module (SKREEM) communi-
cates through its antenna with the Sentry Key transponder using a Radio Frequency (RF) signal. The SKREEM then
listens for a RF response from the transponder through the same antenna. The Sentry Key transponder chip is
within the range of the SKREEM transceiver antenna ring when it is inserted into the ignition lock cylinder. The
SKREEM 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 SKREEM to the Powertrain Control Module
(PCM) over the Controller Area Network (CAN) 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 SKREEM over the CAN 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 CAN data bus by flashing the security indicator on and off.
Each Sentry Key has a unique transponder identification code permanently programmed into it by the manufacturer.
Likewise, the SKREEM has a unique Secret Key code programmed into it by the manufacturer. When a Sentry Key
is programmed into the memory of the SKREEM, the SKREEM stores the transponder identification code from the
Sentry Key, and the Sentry Key learns the Secret Key code from the SKREEM. Once the Sentry Key learns the
Secret Key code of the SKREEM, 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 8 -
ELECTRICAL/VEHICLE THEFT SECURITY/TRANSPONDER KEY - 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 a Diagnostic Trouble Code (DTC) in SKREEM memory if a Sentry Key transponder
problem is detected. The Sentry Key transponder chip can be diagnosed, and any stored DTC can be retrieved
using a diagnostic scan tool. Refer to the appropriate diagnostic information.
STANDARD PROCEDURE
SENTRY KEY TRANSPONDER PROGRAMMING
All Sentry Keys included with the vehicle are pre-programmed to work with the Sentry Key Immobilizer System
(SKIS) when it is shipped from the factory. The Sentry Key REmote Entry Module (SKREEM) can be programmed
to recognize up to a total of eight Sentry Keys. When programming a blank Sentry Key transponder, the key must
first be cut to match the ignition switch lock cylinder in the vehicle for which it will be used. Once the additional or
new key has been cut, the SKREEM must be programmed to recognize it as a valid key. There are two possible
8Q - 92
VEHICLE THEFT SECURITY - SERVICE INFORMATION
WK