Features of the immobilizer design (Fusion)

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

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

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

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

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

2 state - the immobilization function is enabled. In this state, the engine can be blocked, and unlocking is performed by the controller receiving the correct password from the immobilizer control unit.