Keyless Entry: Description and Operation

Sentry Key Remote Entry Module (SKREEM):

The Sentry Key Remote Entry Module (SKREEM) performs the functions of the Sentry Key Immobilizer Module (SKIM) and the Remote Keyless Entry (RKE) module.

SENTRY KEY IMMOBILIZER

Transponder Ring:

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 Controller 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 which picks up the transponder key signal.

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 cylinder. The SKREEM then decrypts the signal and broadcasts the requested remote commands to the appropriate modules in the vehicle over the Controller Area Network (CAN) data bus. A valid transponder 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 window for RKE functions.
Each Sentry Key Remote Entry System (SCREES 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 (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 specific request to the SKREEM. In turn, the SKREEM sends the appropriate request to the CTM to unlock the vehicle doors.

After pressing the lock button on the RKE transmitter, 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 individual access codes (8 transmitters). If the PRNDL is in any position except park, the SKREEM will disable the RKE. Use the DRBIII(R) or the customer programming method to program the RKE system. However, the SKREEM will only allow RKE programming when the ignition is in the ON position, the PRNDL is in park position, and the VTSS (if equipped) is disarmed.