Design

Design

Control module




The immobilizer control module is located above the integrated relay/fusebox to the left of the driver. The casing of the immobilizer control module has different colors. The color depends on which type of engine control module (ECM) it is intended to communicate with.
The engine control module (ECM) cannot activate the fuel injection system when the immobilizer system is inactive. This means that the engine cannot start. To further increase the security the ground to the starter relay is also disconnected. This means that the starter motor cannot be turned.
When the system is activated the immobilizer control module transmits an instruction to the engine control module (ECM) to activate the fuel injection system and to ground the control circuit on the starter relay.
The immobilizer control module communicates with the ignition key transponder via an antenna ring around the ignition switch.
To increase the security and incorporate the components of the system the immobilizer control module must be programmed with three codes before it can be used:
- PIN code to program the key
- code for the engine control module (ECM)
- code for communication with the VGLA (Volvo guard lock and alarm system) control module.
These codes are entered automatically when programming a new control module.
The immobilizer control module also contains a unique identification code (PIN-code). This PIN code is used when making modifications to the system. For example programming new keys or erasing keys if the old ones have been stolen or lost.
The immobilizer system cooperates with the VGLA (Volvo guard lock and alarm system) control module by transmitting a signal to deactivate the alarm if the correct key is inserted in the ignition switch. Each key is programmed with a unique identification code so that the immobilizer control module can recognize each key. This happens at the end of the manufacturing process of the vehicle. These codes must then be learnt by the immobilizer control module. The immobilizer control module can be programmed to recognize up to 6 keys.
The immobilizer control module has built-in diagnostics and diagnostic trouble codes (DTCs) can be read out using VIDA. The immobilizer control module also contains a monitoring function for the connection between the immobilizer control module and the engine control module (ECM). The monitoring function can detect open-circuits, short-circuits to ground or short-circuits to supply voltage.
The immobilizer control module has continuous power supply (+30) from the battery and is grounded via the connection rail (15/6).

Antenna ring




The antenna ring is located around the ignition switch. The antenna ring is used to allow the immobilizer control module to communicate remotely with the ignition key. The magnetic field which is built up in the antenna ring is converted in the key to an electrical current, which means that the key does not require further electrical supply.
The antenna ring is supplied with power and grounded via the immobilizer control module, but is only active when the ignition is switched on.

Relay for the starter motor




The starter motor relay is located in the central electrical unit under the dashboard on the driver's side. The relay receives control voltage from the ignition switch and is grounded via the immobilizer control module. When the immobilizer system is inactive the ground to the relay is disconnected on the control side. This means that the relay cannot draw power and so cannot forward voltage to the starter motor.
When the key is validated the immobilizer control module grounds the control side of the relay and the relay can draw power.

Ignition key




The ignition key contains a communication circuit and a memory circuit. The communication circuit functions as an antenna and voltage source to drive the memory circuit. The communication circuit converts the energy, which is transmitted from the antenna ring, to a direct current to drive the memory circuit. This means that no further voltage drop is necessary. In this context the key cannot "run out"(applies to communication with immobilizer).
The memory circuit contains all further functions needed to communicate with the immobilizer system. For example validation of check messages from the control module and the signal modulation which is transferred to the antenna ring. The key code must be learned by the immobilizer control module for the key to be validated.

Model year 2003-. For vehicles with integrated ignition key/ remote control the following applies:
The key contains an internal button battery. This is necessary for the integrated remote control to transmit the command to the VGLA (Volvo guard lock and alarm system) control module which controls the central locking. The battery must be replaced at regular intervals depending on how often the remote control is used. An indication that the battery is becoming weak is that the range and reaction times of the system begin to degrade.