Operation

OPERATION

When the ignition switch is turned to the On position, the Sentry Key REmote Entry Module (SKREEM), sometimes referred to as the Wireless Control Module (WCM), communicates through its antenna with the Sentry Key transponder using a Radio Frequency (RF) signal. The SKREEM/WCM then listens for a RF response from the transponder through the same antenna. The Sentry Key transponder chip is within the range of the SKREEM/WCM transceiver antenna ring when it is inserted into the ignition lock cylinder. The SKREEM/WCM determines whether a valid key is present in the ignition lock cylinder based upon the response from the transponder. If a valid key is detected, that fact is communicated by the SKREEM/WCM to the Powertrain Control Module (PCM) over the Controller Area Network (CAN) data bus, and the PCM allows the engine to continue running. If the PCM receives an invalid key message, or receives no message from the SKREEM/WCM over the CAN data bus, the engine will be disabled after about two seconds of operation. The Electromechanical Instrument Cluster (EMIC), sometimes referred to as the Cab Compartment Node (CCN), will also respond to the invalid key message on the CAN data bus by flashing the security indicator on and off.

Each Sentry Key has a unique transponder identification code permanently programmed into it by the manufacturer. Likewise, the SKREEM/WCM has a unique Secret Key code programmed into it by the manufacturer. When a Sentry Key is programmed into the memory of the SKREEM/WCM, the SKREEM/WCM stores the transponder identification code from the Sentry Key, and the Sentry Key learns the Secret Key code from the SKREEM/WCM. Once the Sentry Key learns the Secret Key code of the SKREEM/WCM, it is permanently stored in the memory of the transponder. Therefore, once a Sentry Key has been programmed to a particular vehicle, it cannot be used on any other vehicle.

The Sentry Key REmote Entry System (SKREES) performs a self-test each time the ignition switch is turned to the On position, and will store key-related fault information in the form of a Diagnostic Trouble Code (DTC) in SKREEM/WCM memory if a Sentry Key transponder problem is detected. The Sentry Key transponder chip can be diagnosed, and any stored DTC can be retrieved using a diagnostic scan tool. Refer to the appropriate diagnostic information.

Common communication problems:

- Two transponder keys too close together.
- Speed Pass too close to transponder key.
- Loss of PCM communication.
- Failed antenna circuit.