Key identification and starting operation
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2017 BMW X3, 2016 BMW X3, 2015 BMW X3, 2014 BMW X3, and 2013 BMW X3. However, it is still accessible from the selected car via links, so may be relevant.
The following procedure takes place after identification of the vehicle key:
- The vehicle key transmits the key data to the CAS/FEM/BDC control unit.
- The CAS/FEM/BDC control unit checks the correctness of the key data and only then enables activation of the starter motor by the engine control unit.
- The engine control unit calculates a request from a random number and the secret key. The engine control unit transmits this request to the CAS/FEM/BDC.
- The CAS/FEM/BDC uses the request and the secret key to calculate the confirmation. The confirmation is transmitted from the CAS/FEM/BDC to the engine control unit.
- The engine control unit itself also calculates the confirmation that the CAS/FEM/BDC expects. The engine control unit then checks that the confirmation it receives from the CAS/FEM/BDC matches the confirmation it has calculated itself.
- If the confirmations match, the engine start is enabled.