
MESSAGE SYSTEMS
TABLE OF CONTENTS
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MESSAGE CENTER......................... 1OVERHEAD CONSOLE....................... 2
MESSAGE CENTER
TABLE OF CONTENTS
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MESSAGE CENTER
REMOVAL...............................1INSTALLATION............................1
MESSAGE CENTER
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Using a trim stick (special tool #C-4755) or
equivalent, gently pry up on the front side of the
message center and lift out of instrument panel open-
ing.
(3) Disconnect the wire connector from the back of
message center.
(4) Remove message center from vehicle.NOTE: If the message center lamp needs replacing,
twist out defective bulb socket and replace with a
known good bulb and socket.
INSTALLATION
(1) Connect the wiring connector to message cen-
ter.
(2) Place message center in position on instrument
panel and firmly snap into place.
(3) Connect battery negative cable.
RSMESSAGE SYSTEMS8M-1

the OFF position. Replace the first valid Sentry Key
in the ignition lock cylinder with the second valid
Sentry Key and turn the ignition switch back to the
ON position. The second valid Sentry Key must be
inserted within 15 seconds of removing the first valid
Sentry key.
(4) About ten seconds after the completion of Step
3, the indicator light will start to flash and a single
audible chime tone will sound to indicate that the
system has entered the9Customer Learn9program-
ming mode.
(5) Within sixty seconds of entering the9Customer
Learn9programming mode, turn the ignition switch
to the OFF position, replace the valid Sentry Key
with a blank Sentry Key transponder, and turn the
ignition switch back to the ON position.
(6) About ten seconds after the completion of Step
5, a single audible chime tone will sound and the
indicator light will stop flashing and stay on solid for
three seconds and then turn off to indicate that the
blank Sentry Key has been successfully programmed.
The SKIS will immediately exit the9Customer
Learn9programming mode and the vehicle may be
started using the newly programmed Sentry Key.
These steps must be completed in their entirety for
each additional Sentry Key to be programmed. If any
of the above steps are not completed in the given
sequence, or within the allotted time, the SKIS will
exit the9Customer Learn9programming mode and
the programming will be unsuccessful. The SKIS will
also automatically exit the9Customer Learn9pro-
gramming mode if:
²It sees a non-blank Sentry Key when it should
see a blank.
²If it has already programmed eight (8) valid
Sentry Keys.
²If the ignition switch is turned to the OFF posi-
tion for more than about fifty (50) seconds.
NOTE: If you attempt to start the vehicle while in
ªCustomer Learnº mode (LED flashing), the vehicle
will behave as though an invalid key is being used
(i.e. the engine will stall after two (2) seconds of
running). No faults will be logged.
NOTE: Once a Sentry Key has been programmed to
a particular vehicle, it cannot be used on any other
vehicle.VTSS/SKIS INDICATOR LAMP
DESCRIPTION
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.
OPERATION
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 oper-
ate 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 mes-
sage 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 the9Cus-
tomer Learn9mode. Refer to Electrical, Vehicle Theft
Security, Transponder Key, Standard Procedure -
Transponder Programming for more information on
the9Customer Learn9mode. If the light comes on
and stays on after the power-up test, diagnosis of the
SKIS should be performed using a DRB IIItscan tool
and the appropriate Body Diagnostic Procedures
manual. The light is not a serviceable component.
RSVEHICLE THEFT SECURITY8Q-5
TRANSPONDER KEY (Continued)

message the PCM will terminate engine operation,
or allow the engine to continue to operate.
3.2.7 SKIM ON-BOARD DIAGNOSTICS
The SKIM has been programmed to transmit and
monitor many different coded messages as well as
PCI Bus messages. This monitoring is called On
Board Diagnosis.
Certain criteria must be met for a diagnostic
trouble code to be entered into the SKIM memory.
The criteria may be a range of; Input voltage, PCI
Bus message, or coded messages to the SKIM. If all
of the criteria for monitoring a circuit or function
are met and a fault is sensed, a diagnostic trouble
code will be stored in the SKIM memory.
3.2.8 SKIS OPERATION
When ignition power is supplied to the SKIM, the
SKIM performs an internal self-test. After the self-
test is completed, the SKIM energizes the antenna
(this activates the transponder chip) and sends a
challenge to the transponder chip. The transponder
chip responds to the challenge by generating an
encrypted response message using the following:
Secret Key -This is an electronically stored
value (identification number) that is unique to each
SKIS. The secret key is stored in the SKIM, PCM
and all ignition key transponders.
Challenge- This is a random number that is
generated by the SKIM at each ignition key cycle.
The secret key and challenge are the two vari-
ables used in the algorithm that produces the
encrypted response message. The transponder uses
the crypto algorithm to receive, decode and respond
to the message sent by the SKIM. After responding
to the coded message, the transponder sends a
transponder I.D. message to the SKIM. The SKIM
compares the transponder I.D. to the available valid
key codes in the SKIM memory (8 key maximum at
any one time). After validating the key ignition the
SKIM sends a PCI Bus message called a Seed
Request to the engine controller then waits for a
PCM response. If the PCM does not respond, the
SKIM will send the seed request again. After three
failed attempts the SKIM will stop sending the seed
request and store a trouble code. If the PCM sends
a seed response, the SKIM sends a valid/invalid key
message to the PCM. This is an encrypted message
that is generated using the following:
VIN -Vehicle Identification Number
Seed -This is a random number that is generated
by the PCM at each ignition key cycle.
The VIN and seed are the two variables used in
the rolling code algorithm that encrypts the valid/
invalid key message. The PCM uses the rolling code
algorithm to receive, decode and respond to the
valid/invalid key message sent by the SKIM. Aftersending the valid/invalid key message the SKIM
waits 3.5 seconds for a PCM status message from
the PCM. If the PCM does not respond with a valid
key message to the SKIM, a fault is detected and a
trouble code is stored.
The SKIS incorporates a VTSS LED located on
the instrument panel upper cover. The LED re-
ceives switched ignition voltage and is hardwired to
the body control module. The LED is actuated when
the SKIM sends a PCI Bus message to the body
controller requesting the LED on. The body control-
ler then provides the ground for the LED. The
SKIM will request VTSS LED operation for the
following:
± bulb checks at ignition on
± to alert the vehicle operator to a SKIS mal-
function
± customer key programming mode
For all faults except transponder faults and VTSS
LED remains on steady. In the event of a transpon-
der fault the LED flashes at a rate of 1 Hz (once per
second). If a fault is present the LED will remain on
or flashing for the complete ignition cycle. If a fault
is stored in SKIM memory which prevents the
system from operating properly, the PCM will allow
the engine to start and run (for 2 seconds) up to six
times. After the sixth attempt, the PCM disables
the starter relay until the fault is corrected.
3.2.9 PROGRAMMING THE POWERTRAIN
CONTROL MODULE
Important Note:Before replacing the PCM for a
failed driver, control circuit or ground circuit, be
sure to check the related component/circuit integ-
rity for failures not detected due to a double fault in
the circuit. Most PCM driver/control circuit failures
are caused by internal failure to components (i.e.
12-volt pull-ups, drivers and ground sensors). These
failures are difficult to detect when a double fault
has occurred and only one DTC has set.
NOTE: IF THE PCM AND THE SKIM ARE
REPLACED AT THE SAME TIME, PROGRAM
THE VIN INTO THE PCM FIRST. ALL VEHICLE
KEYS WILL THEN NEED TO BE REPLACED
AND PROGRAMMED TO THE NEW SKIM.
The SKIS Secret Key is an I.D. code that is
unique to each SKIS. This code is programmed and
stored in the SKIM, engine controller and transpon-
der chip (ignition key). When replacing the PCM it
is necessary to program the secret key into the
PCM.
1. Turn the ignition on (transmission in park/
neutral).
2. Use the DRB and select THEFT ALARM, SKIM
then MISCELLANEOUS.
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GENERAL INFORMATION