SENTRY KEY IMMOBILIZER
The Sentry Key Immobilizer System (SKIS)
authenticates an electronically coded Transponder
Key placed into the ignition and sends a valid/invalid
key message to the Engine Control Module (ECM)
based upon the results. The “VALID/INVALID KEY”
message communication is performed using a rolling
code algorithm. A “VALID KEY” message must be
sent to the ECM within two seconds of ignition ON
to free the engine from immobilization. This Control-
ler Area Network (CAN) data bus message is sent to
the ECM after first going through the SKREEM. The
SKREEM is located behind the instrument cluster
and has a separately mounted antenna ring mounted
around the ignition cylinder (Fig. 3) which picks up
the transponder key signal.
REMOTE KEYLESS ENTRY (RKE)
The RKE transmitter uses radio frequency signals
to communicate with the Sentry Key Remote Entry
Module (SKREEM). The SKREEM is hardwired to
the Central Timer Module (CTM). When the operator
presses a button on the transmitter, it sends a spe-
cific request to the SKREEM. In turn, the SKREEM
sends the appropriate request to the CTM to unlock
the vehicle doors.
OPERATION
SENTRY KEY IMMOBILIZER
The Sentry Key Remote Entry Module (SKREEM)
receives an encrypted Radio Frequency (RF) signal
from the transponder key which is read by the
remotely mounted antenna ring at the ignition cylin-
der. The SKREEM then decrypts the signal and
broadcasts the requested remote commands to the
appropriate modules in the vehicle over the Control-
ler Area Network (CAN) data bus. A valid transpon-
der key ID must be incorporated into the RF signal
in order for the SKREEM to pass the message on to
the appropriate modules.
Automatic transponder key synchronization is done
by the SKREEM if a valid transponder key is
inserted into the ignition cylinder, and the ignition is
turned ON. This provides a maximum operation win-
dow for RKE functions.
Each Sentry Key Remote Entry System (SKREES)
consists of a SKREEM, an antenna ring mounted
around the ignition cylinder, and a transponder key.
Each system has a secret key code unique to that
system. The secret key is electronically coded in the
SKREEM and in all programmed transponder keys.
It is used for immobilization and RKE functions for
data security. In addition, each transponder key will
have a unique identification.
REMOTE KEYLESS ENTRY
After pressing the lock button on the RKE trans-
mitter, all of the door locks will lock, the illuminated
entry will turn off (providing all doors are closed),
and the VTSS (if equipped) will arm. After pressing
the unlock button, on the RKE transmitter, one time,
the driver door lock will unlock, the illuminated
entry will turn on the courtesy lamps, and the VTSS
(if equipped) will disarm. After pressing the unlock
button a second time, the remaining door locks will
unlock.
The SKREEM is capable of retaining up to 8 indi-
vidual access codes (8 transmitters). If the PRNDL is
in any position except park, the SKREEM will dis-
able the RKE. Use the DRBIIIt or the customer pro-
gramming method to program the RKE system.
However, the SKREEM will only allow RKE pro-
gramming when the ignition is in the ON position,
the PRNDL is in park position, and the VTSS (if
equipped) is disarmed.
REMOVAL
SENTRY KEY REMOTE ENTRY MODULE
(1) Open hood, disconnect and isolate the battery
negative cable.
(2) Wait two minutes for the system reserve capac-
itor to discharge before beginning any system or com-
ponent service.
(3) Remove top cover - cluster (Refer to 23 -
BODY/INSTRUMENT PANEL/TOP COVER - CLUS-
TER - REMOVAL).
Fig. 3 TRANSPONDER RING
VA VEHICLE THEFT SECURITY 8Q - 3
SENTRY KEY REMOTE ENTRY MODULE (Continued)
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