Key identification and starting operation

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.