Description And Operation: Operation

In vehicles not equipped with the optional PEKG system, when the status of the ignition transitions to On, the BCM communicates through its antenna with the Sentry Key transponder using a Radio Frequency (RF) signal. The BCM then listens for a RF response from the transponder through the same antenna. The Sentry Key transponder chip is within the range of the BCM transceiver antenna ring when it is inserted into the ignition lock cylinder. The BCM determines whether a valid key is present in the ignition lock cylinder based upon the response from the transponder.

In vehicles equipped with the optional PEKG system, when the status of the ignition switch (KIN) transitions to On it provides a hardwired input to the BCM and an electronic message input to the RFH over a dedicated Local Interface Network (LIN) data bus. The RFH relies upon several Low Frequency (LF) antenna units to challenge the Sentry Key transponders using a LF signal, then monitors responses from the Sentry Key transponders received as Very High Frequency (VHF) signals. The RFH determines whether a valid key is present based upon the response from the transponder.

If a valid key is detected, an electronic valid key  message is broadcast by the BCM or the RFH 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 electronic invalid key  message from the BCM or the RFH, or receives no message from the BCM or the RFH over the CAN data bus, the engine will be disabled after about two seconds of operation. The Instrument Panel Cluster (IPC) will also respond to the electronic invalid key  message on the CAN data bus by flashing the security indicator On and Off.