System Working In Nominal Mode

The nominal mode supposes that the different elements of the system are programmed (synchronized Immobilizer system)

• The secret key code is programmed in BCM and keys memory
• The learnt keys identifiers are stored in BCM memory
• The corresponding VIN-code is learnt and memorized in the ECM memory

1. Ignition ON transition phase:

   Introducing a valid key into the steering lock, the system wakes up and BCM control unit sends to the key transponder a random data question (named challenge).

   Transponder and BCM calculate the corresponding response by the encryption algorithm, and the response is sent back by transponder to the BCM which compares it with its own response.

   If they match, the BCM Immobilizer function switches in released state.

   If they do not match, the BCM Immobilizer function switches in blocked state.

   Then, turning ON the ignition, the BCM switches its internal K-line relay to isolate BCM and ECM control units from the system K-line, and in order to allow communication between BCM and ECM during a predefined tuned time window.

   CAUTION: If the user waits for more than a predefined tuned time (10 seconds) between inserting of valid key and turning ON the ignition, the BCM Immobilizer function switches back in blocked state after this delay;
   In this case, or if transponder communication has failed, a new communication with key transponder is carried out at Ignition ON transition to evaluate again Immobilizer state.
2. BCM-ECM Communication phase:

   After this first " Ignition ON transition" phase, a communication between BCM and ECM control units takes place.

   Turning ON the ignition, the ECM control unit controls the engine in a normal way for starting and running, and starts communication with the BCM, sending a VIN request to the BCM and waiting for a valid release message from it until the release time period has ended.

   In case of BCM Immobilizer function state is " blocked", the BCM answer is the " no release" message. ECM enters into the locked state, which causes the activation of the immobilization actions of the engine.

   In case of BCM Immobilizer function state is " released", the BCM answer is the " release" message, including the information " BCM in learnt mode" and the VIN-code.

   • If VIN-code received by the BCM is the same as ECM VIN-code, and if MIN-code received by the BCM is the same as ECM MIN-code, ECM enters in the unlocked state, which allows continuing the running of the engine.
   • If VIN-code received by the BCM is different than ECM VIN-code, or if MIN-code received by the BCM is the different than ECM MIN-code, ECM enters in the locked state, which causes the activation of the immobilization actions of the engine.
   • If the ECM doesn't receive a response message from the BCM within the release time period, ECM enters in the locked state, which causes the activation of the immobilization actions of the engine.
   • If the BCM doesn't receive any ECM request within the defined time, the BCM Immobilizer function switches in released state.
   • If the ECM request contains a MIN-code different than BCM MIN-code, the BCM Immobilizer function switches in blocked state.
3. Ignition OFF transition phase:

   Turning OFF the ignition, the BCM Immobilizer function stays in released state (if already in this state) during a predefined tuned time (10 seconds), allowing a fast restart of engine without key transponder communication, and then returns in blocked state.

   After that, to restart the engine, a new communication with key transponder will be carried out:

   • By removing and inserting again the key in the steering lock
   • By turning ON again the ignition