Key, Transponder: Operation

When the ignition switch is turned to the On position, the Body Control Module (BCM) communicates through its antenna with the Sentry Key transponder using a Radio Frequency (RF) signal. The BCM waits for an RF response from the transponder through the same antenna when the Sentry Key transponder chip is within the range of the BCM transceiver antenna ring and is inserted into the ignition lock cylinder. The BCM determines whether a valid key is present in the ignition lock cylinder based upon the transponder's response. When a valid key is detected, an electronic valid key  message is broadcast by the BCM 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 receives no message from the BCM 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.