System Overview

System overview

Immobilizer




The Immobilizer increases the level of security of the car. The car cannot be used when it is unattended. The Immobilizer system has a preventative function which means that the fuel and ignition systems cannot operate unless the immobilizer system is active. When the system is inactive it is impossible to start the vehicle in a short time without using the correct ignition key.
The system is deactivated at the latest 3 seconds after the ignition has been switched off. This means that the vehicle cannot be used whether it is locked or not.
The immobilizer system is made up of:
- immobilizer control module
- engine control module (ECM)
- antenna ring, mounted around the ignition switch
- ignition key
- starter relay
- indicator lamp in the combined instrument panel.
Communication between the immobilizer control module, the engine control module (ECM) and the ignition key is encrypted. This means that the system cannot be "hot wired".
The system can be installed regardless of whether a VGLA (Volvo guard lock and alarm system) system is installed in the vehicle or not. If an alarm system is installed, the immobilizer system and the lock and alarm system operate together.
The status of the immobilizer system can be indicated in two ways:
- via the indicator lamp on top of the dashboard (if the vehicle does not have an alarm)
- via an indicator lamp in the combined instrument panel.
The indicator lamp is controlled by the VGLA (Volvo guard lock and alarm system) control module if the alarm is installed. Otherwise the lamp is directly connected to the immobilizer control module.
The indicator lamp in the combined instrument panel lights when the ignition is switched on to indicate that the system is being checked. The lamp goes out after approximately 3 seconds if no faults are detected. If a fault in the system is identified the lamp remains lit. If the ignition key identity check has failed or an attempt was made to start the vehicle using the wrong key, the indicator lamp will start to flash approximately 4 times per second and the vehicle will not start.
When installed in the vehicle the immobilizer control module and the engine control module (ECM) will "marry". This occurs by the engine control module (ECM) learning the immobilizer control module code the first time the ignition is switched on after the control modules have been connected to each other.
This means that neither an immobilizer control module, engine control module (ECM) nor a VGLA (Volvo guard lock and alarm system) control module can be moved between cars.
The immobilizer control module and VGLA (Volvo guard lock and alarm system) control module connect to each other in the same way when a new immobilizer control module is programmed.

Note! In vehicles with the Melco2 (B4184SJ) engine management system the "marriage" occurs immediately when a new immobilizer control module or new engine control module (ECM) is programmed using VIDA.

Terminology
System active: Correct key in ignition switch. Engine permitted to start.
System inactive: Key not in ignition switch, immobilizer control module inactive, the engine cannot be started.

Signals
The table below summarizes the input signals to and output signals from the immobilizer control module. The illustration below displays the same information with the Volvo component designations.