OPERATION
The Sentry Key Remote Entry Module (SKREEM) has the following functions: receiving and evaluating the Radio
Frequency (RF) keyless entry remote signal, actuation of door locks in conjunction with the Central Locking Pump/
Security System Module, and enabling the vehicle theft security alarm with confirmation via the turn signals. When
the RKE transmitter is operated, an RF signal is transmitted. If the SKREEM recognizes the RF signal as valid, it
actuates the Central Locking Pump/Security System Module through the Body Control Module. The vehicle is then
locked or unlocked through the power locks system. Connected to the SKREEM is a Sentry Key Antenna Ring
which surrounds the ignition lock cylinder. When the ignition is switched on, the Sentry Key Antenna Ring is supplied
with power. A data block is transmitted inductively via the Sentry Key Antenna Ring to the SKREEM and then
on to the Powertrain Control Module. If the antenna ring data block content is invalid or if vehicle battery power is
too low to build up enough power for the antenna ring, the Powertrain Control Module will not receive the proper
signal. This is displayed with the message “Start Error” in the Instrument Cluster.
The SKREEM contains an RF transceiver and a microprocessor. The SKREEM transmits RF signals to and receives
RF signals from the ignition key transponder through a tuned Sentry Key Antenna Ring that is wired to the
SKREEM. If the Sentry Key Antenna Ring is not mounted properly around the ignition lock cylinder housing, communication
problems between the SKREEM and the ignition key may arise. These communication problems will
result in ignition key transponder-related faults. The SKREEM also communicates over the Controller Area Network
(CAN) data bus with the Powertrain Control Module (PCM), the Instrument Cluster, the Body Control Module (BCM),
and/or the DRB III
scan tool.
The SKREEM retains in memory the ID numbers of any ignition key transponder that is programmed into it. For
added system security each SKREEM is programmed with a unique secret key code. This code is stored in memory,
sent over the CAN data bus to the PCM, and is encoded to the transponder of every ignition key that is programmed
into the SKREEM.
In the event that a SKREEM replacement is required, the secret key code can be transferred to the new SKREEM
from the PCM using the DRB III
scan tool and the ignition key system replacement programming procedure.
Proper completion of the ignition key system initialization will allow the existing ignition keys to be programmed into
the new SKREEM so that new keys will not be required. In the event that the original secret key code cannot be
recovered, SKREEM replacement will also require new ignition keys. The DRB III
scan tool will alert the technician
during the key reprogramming procedure if new ignition keys are required.
The sentry key system performs a self-test each time the ignition switch is turned to the ON/RUN position and will
store fault information in the form of Diagnostic Trouble Codes (DTCs) in SKREEM memory if a system malfunction
is detected. The SKREEM can be diagnosed and any stored DTCs can be retrieved using a DRB III
scan tool.
Refer to the appropriate diagnostic information.