Design features of the immobilizer

An immobilizer is installed on Ford Fusion cars. This electronic device is designed to prevent unauthorized starting of the engine by breaking the electrical circuits of the engine control system.

The immobilizer consists of a control unit and a control lamp in the instrument cluster, a communication coil in the ignition lock, a working key in the remote control. The immobilizer operating modes are displayed by turning on the signaling device and the signals of the buzzer built into it.

The immobilizer control unit is connected to the controller via the diagnostic line. The control unit has a built-in relay that connects the diagnostic block to the controller or disables it. If a diagnostic tool is not connected to the diagnostic block, the relay opens the diagnostic circuit and the line is used to communicate with the controller and the control unit. When the device is connected to the diagnostic block, the relay closes the diagnostic circuit, which allows the exchange of information between the device and the controller. However, the immobilizer control unit has priority over the diagnostic tool when working with the controller, if necessary, the control unit interrupts the connection between the controller and the tool (for example, to exchange information between the control unit and the controller when starting the engine).

The immobilizer control unit and the controller can be in one of two states:

1 state - the immobilization function is disabled. In this state, the immobilizer control unit is turned off, there is no communication between it and the controller, engine blocking is impossible;

2 state - the immobilization function is enabled. In this state, it is possible to block the engine, unlocking is carried out by receiving the correct password from the immobilizer control unit by the controller.