5.2.1 RKE Operation

Once one or more fobs are paired with the system, test the RKE using the CARS PC application running on the host PC as follows:
  1. If not done so already, follow the procedure detailed in CARS Kit PC Evaluation Utility.
  2. Navigate to View > RKE Messaging. The RKE Message Status window shows the following data fields:
    Figure 5-2. RKE Message Status Window
    • “RF Message S/N” – Displays the UID returned by the fob. The same UID value for a given fob displays in the learned fobs section of the System Configuration window.

    • “Log File” – Selecting this check box creates a new record line in a CSV document for each received message when it is selected.

    • “RF Message Counter” – Displays the rolling code message counter value sent to the vehicle. This value is incremented for every key push. All RKE commands increment the counter value. The counter is checked against a window of valid counts on the vehicle side to prevent recording and replaying of past RKE messages from being accepted as valid, which is commonly referred to as a replay attack.
    • “RF Message Command” – Displays the most recent RKE command received from the fob.
    • “RF Message MAC” – Displays the received 4-byte (32-bit) Message Authentication Code (MAC).
    • “RF Message Result” – Displays the result of the comparison between the expected MAC (computed using AES-128) and the received MAC.
    • “RF Channel” – Displays the RF channel that received the message.
    • “RF RSSI” – The signal strength measured at the RF transceiver board displays in three formats. There is a decimal representation read directly from the RF transceiver device followed by a calculated dBm value. Finally, there is a bar graph that provides visual representation.
  3. Press any of the RKE buttons to send the RKE message. For more details, refer to Remote Keyless Entry Operation.