Immobilizer — design features (Renault Sandero 1)

An immobilizer is installed on Renault/Dacia Sandero vehicles - an electronic device designed to prevent unauthorized engine starting by breaking the electrical circuits of the engine control system.

The immobilizer consists of a control unit, a communication coil in the ignition switch (transponder rings), keys and a control lamp in the instrument cluster. The immobilizer operating modes are displayed by turning on the signal lamp.

The immobilizer control unit is connected to the controller via a diagnostic line. The control unit includes 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 information to be exchanged 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).

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