Antenna, Sentry Key: Operation

The Sentry Key Immobilizer System (SKIS) control circuitry integral to the Body Control Module (BCM) includes a Radio Frequency (RF) transceiver. The BCM circuitry transmits RF signals to, and receives RF signals from the Sentry Key transponder through the tuned Sentry Key antenna enclosed within the molded plastic antenna housing. If this antenna is not mounted properly around the ignition lock cylinder housing, communication problems between the BCM control circuitry and the transponder may arise. These communication problems will result in Sentry Key transponder-related faults.

When the status of the ignition switch transitions to On, the BCM control circuitry transmits an RF signal to the transponder in the ignition key. The BCM then waits for an RF signal response from the transponder. If the response received identifies the key as valid, the BCM control circuitry sends a valid key message to the Electric Vehicle Control Unit (EVCU) over the Controller Area Network (CAN) data bus. If the response received identifies the key as invalid, or if no response is received from the key transponder, the BCM sends an invalid key message to the EVCU. The EVCU will enable or disable electric vehicle drive unit operation based upon the status of the BCM messages. It is important to note that the default condition in the EVCU is an invalid key; therefore, if no message is received from the BCM by the EVCU, the electric vehicle drive unit will be disabled and the vehicle is immobilized.

The BCM performs a self-test each time the status of the ignition switch transitions to On, and will store fault information in the form of a Diagnostic Trouble Code (DTC) in BCM memory if a system malfunction is detected. The Sentry Key antenna can be diagnosed, and any stored DTC can be retrieved using a diagnostic scan tool. Refer to the appropriate diagnostic information.