Operation

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(R) 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(R) 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(R) 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(R) scan tool. Refer to the appropriate diagnostic information.