Immobiliser (Function): Description and Operation

Function

 

The transmitter (transponder) in the handle of the vehicle key does not require either batteries nor maintenance. The voltage is supplied cordlessly by the immobiliser control unit.

 

 

When the ignition is switched on, the transponder key sends an identification code (transponder code) to the immobiliser control unit.

 

 

Once the transponder code is recognized, the immobiliser control unit sends a coded signal (imo signal) to the engine control unit (for petrol and 25 DT diesel engines).

For diesel engines without electronic engine management, the immobiliser control unit is connected to the control unit for the fuel cutoff solenoid valve.

 

 

At this point, the received code is compared once again with the stored code.

 

 

If the received imo signal does not match the stored code, all relevant engine functions are switched off by the engine control unit or the diesel feed is blocked.

 

 

If there is a malfunction (incorrect transponder, no communication), the engine telltale in the instrument panel flashes. The relevant trouble code is blocked.

 

 

If there is a malfunction, the ignition must be switched off and on again before starting is attempted again.

 

 

·   Service

 

The immobiliser control unit is capable of diagnosis with TECH 1. To protect it against unauthorized tampering, the immobiliser control unit can only be programmed after entering a security code (see section 8.1.4.2, "Control Unit").