When the ignition switch is turned to the ON or
START positions, the SKIM transmits an RF signal
to excite the Sentry Key transponder. The SKIM then
listens for a return RF signal from the transponder
of the Sentry Key that is inserted in the ignition lock
cylinder. If the SKIM receives an RF signal with
valid “Secret Key” and transponder identification
codes, the SKIM sends a “valid key” message to the
PCM over the PCI bus. If the SKIM receives an
invalid RF signal or no response, it sends “invalid
key” messages to the PCM. The PCM will enable or
disable engine operation based upon the status of the
SKIM messages.
The SKIM also sends messages to the BCM which
controls the VTSS indicator LED. The SKIM sends
messages to the BCM to turn the LED on for about
three seconds when the ignition switch is turned to
the ON position as a bulb test. After completion of
the bulb test, the SKIM sends bus messages to keep
the LED off for a duration of about one second. Then
the SKIM sends messages to turn the LED on or off
based upon the results of the SKIS self-tests. If the
VTSS indicator LED comes on and stays on after the
bulb test, it indicates that the SKIM has detected a
system malfunction and/or that the SKIS has become
inoperative.
If the SKIM detects an invalid key when the igni-
tion switch is turned to the ON position, it sends
messages to flash the VTSS indicator LED. The
SKIM can also send messages to flash the LED and
to generate a single audible chime tone. These func-
tions serve as an indication to the customer that the
SKIS has been placed in its “Customer Learn” pro-
gramming mode. See Sentry Key Immobilizer System
Transponder Programming in this section for more
information on the “Customer Learn” programming
mode.
For diagnosis or initialization of the SKIM and the
PCM, a DRB IIIt scan tool and the proper Body
Diagnostic Procedures Manual are required. The
SKIM cannot be repaired and, if faulty or damaged,
the unit must be replaced.
SENTRY KEY IMMOBILIZER SYSTEM
INDICATOR LAMP
DESCRIPTION
The Sentry Key Immobilizer System (SKIS) uses
the Vehicle Theft Security System (VTSS) indicator
LED to give an indication when the SKIS is faulty or
when the vehicle has been immobilized due to the
use of an invalid ignition key. The LED is controlled
by the BCM based upon messages received from the
Sentry Key Immobilizer Module (SKIM). The VTSS/
SKIS indicator LED is hard wired directly to the
BCM.
OPERATION
The SKIM sends messages to the BCM to turn the
LED on for about three seconds when the ignition
switch is turned to the ON position as a bulb test.
After completion of the bulb test, the SKIM sends
bus messages to the BCM to keep the LED off for a
duration of about one second. Then the SKIM sends
messages to the BCM to turn the LED on or off
based upon the results of the SKIS self-tests. If the
VTSS indicator LED comes on and stays on after the
bulb test, it indicates that the SKIM has detected a
system malfunction and/or that the SKIS has become
inoperative. If the SKIM detects an invalid key when
the ignition switch is turned to the ON position, it
sends messages to the BCM to flash the VTSS indi-
cator LED.
The SKIM can also send messages to the BCM to
flash the LED and to generate a single audible chime
tone. These functions serve as an indication to the
customer that the SKIS has been placed in its “Cus-
tomer Learn” programming mode. See Sentry Key
Immobilizer System Transponder Programming in
this section for more information on the “Customer
Learn” programming mode.
The VTSS indicator LED is housed in the Auto-
matic Temperature Control (ATC) Sun Sensor located
in the instrument panel top cover. Refer to Group 8E
- Instrument Panel and Systems for service of ATC
Sun Sensor. If the VTSS indicator LED comes on and
stays on after the bulb test function, diagnosis of the
SKIS should be performed with a DRB IIIt scan tool
and the proper Body Diagnostic Procedures Manual.
SENTRY KEY IMMOBILIZER TRANSPONDER
DESCRIPTION
The Sentry Key Immobilizer System (SKIS) uses a
transponder that is integral to each of two ignition
key that are supplied with the vehicle when it is
shipped from the factory. The transponder chip is
insulated within a nylon mount inserted in the head
of the key, and invisible beneath a molded rubber
cap.
OPERATION
Each Sentry Key transponder has a unique tran-
sponder identification code programmed into it by the
manufacturer. The Sentry Key Immobilizer Module
(SKIM) has a unique “Secret Key” code programmed
into it by the manufacturer. When a Sentry Key
transponder is programmed into the memory of the
SKIM, the SKIM learns the transponder identifica-
tion code from the transponder, and the transponder
learns the “Secret Key” code from the SKIM. Each of
these codes is stored within the transponder and in
the nonvolatile memory of the SKIM. Therefore,
LH VEHICLE THEFT/SECURITY SYSTEMS 8Q - 3
DESCRIPTION AND OPERATION (Continued)
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