Refer to the appropriate Powertrain Diagnostic Man-
ual and the DRBIII
t scan tool.
(1) Install PCM module to the mounting bracket.
(2) Install electrical connectors and lock.
(3) Install the splash shield.
(4) Lower vehicle.
(5) Connect the negative battery cable.
(6) Using DRBIII
t scan tool, program mileage and
vehicle identification number (VIN) into PCM. Refer
to the DRBIII
t scan tool and the appropriate Power-
train Diagnostic Manual.
SENTRY KEY IMMOBILIZER
MODULE
DESCRIPTION
The Sentry Key Immobilizer Module (SKIM) con-
tains a Radio Frequency (RF) transceiver and a
microprocessor. The SKIM retains in memory the ID
numbers of any Sentry Key that is programmed to it.
The maximum number of keys that may be pro-
grammed to each module is eight (8). The SKIM also
communicates over the Programmable Communica-
tion Interface (PCI) data bus with the Powertrain
Control Module (PCM), the Body Control Module
(BCM), the Mechanical Instrument Cluster (MIC),
and the DRB III
t scan tool. The SKIM transmits and
receives
RF
signals
through
a
tuned
antenna
enclosed within a molded plastic ring formation that
is integral to the SKIM housing. When the SKIM is
properly
installed
on
the
steering
column,
the
antenna ring fits snugly around the circumference of
the ignition lock cylinder housing. If this ring is not
mounted
properly,
communication
problems
may
arise in the form of transponder-related faults.
For added system security, each SKIM is pro-
grammed with a unique
9Secret Key9 code. This code
is stored in memory and is sent over the PCI bus to
the PCM and to each key that is programmed to
work with the vehicle. The
9Secret Key9 code is there-
fore a common element found in all components of
the Sentry Key Immobilizer System (SKIS). In the
event that a SKIM replacement is required, the
9Secret Key9 code can be restored from the PCM by
following the SKIM replacement procedure found in
the DRB III
t scan tool. Proper completion of this
task will allow the existing ignition keys to be repro-
grammed. Therefore, new keys will NOT be needed.
In the event that the original
9Secret Key9 code can
not be recovered, new ignition keys will be required.
The DRB III
t scan tool will alert the technician if
key replacement is necessary. Another security code,
called a PIN, is used to gain secured access to the
SKIM for service. The SKIM also stores in its mem-
ory the Vehicle Identification Number (VIN), which it
learns through a bus message from the assembly
plant tester. The SKIS scrambles the information
that is communicated between its components in
order to reduce the possibility of unauthorized SKIM
access and/or disabling.
OPERATION
When the ignition switch is moved to the RUN
position, the Sentry Key Immobilizer Module (SKIM)
transmits an Radio Frequency (RF) signal to the
transponder in the ignition key. The SKIM then
waits for a response RF signal from the transponder
in the key. If the response received identifies the key
as valid, the SKIM sends a
9valid key9 message to
the Powertrain Control Module (PCM) over the Pro-
grammable Communication Interface (PCI) data bus.
If the response received identifies the key as invalid
or no response is received from the transponder in
the ignition key, the SKIM sends an
9invalid key9
message to the PCM. The PCM will enable or disable
engine operation based upon the status of the SKIM
messages. It is important to note that the default
condition in the PCM is
9invalid key.9 Therefore, if no
response is received by the PCM, the engine will be
immobilized after two (2) seconds of running.
The SKIM also sends indicator light status mes-
sages to the Mechanical Instrument Cluster (MIC) to
operate the light. This is the method used to turn the
light ON solid or to flash it after the indicator light
test is complete to signify a fault in the SKIS. If the
light comes ON and stays ON solid after the indica-
tor light test, this signifies that the SKIM has
detected a system malfunction and/or that the SKIS
has become inoperative. If the SKIM detects an
invalid key OR a key-related fault exists, the indica-
tor light will flash following the indicator light test.
The SKIM may also request an audible chime if the
customer key programming feature is available and
the procedure is being utilized (Refer to 8 - ELEC-
TRICAL/VEHICLE THEFT SECURITY/TRANSPON-
DER KEY - STANDARD PROCEDURE).
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove Lower Instrument Panel Cover. Refer
to Body, Instrument Panel, Lower Instrument Panel
Cover, Removal.
(3) Remove the steering column upper and lower
shrouds. Refer to Steering, Column, Column Shroud,
Removal.
(4) Disengage the steering column wire harness
from the Sentry Key Immobilizer Module (SKIM).
(5) Remove the one screws securing the SKIM to
the steering column.
8E - 18
ELECTRONIC CONTROL MODULES
RS
POWERTRAIN CONTROL MODULE (Continued)