Specifications

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GENERAL OPERATION
INTRODUCTION
The General Motors Immobiliser is used in conjunction with the vehicle
engine management electronics to immobilise the vehicle. The first
systems were fitted to Petrol vehicles and subsequently fitted to Diesel
vehicles from 95½ Model Year.
The immobiliser system is independent, and can be diagnosed separately .
The system is also operated independently from the central locking
system, and it’s main function is to inhibit starting.
Immobiliser Control Unit
The immobilisers function is to transmit the start signal to the engine
management ECU after it has read the key fob code. If the code is
recognised the immobiliser sends the signal and the ECU compares the
code with what is programmed. If the signal is incorrect the engine which
is allowed to start initially is then switched OFF. If there is a malfunction
then the engine check light mounted in the instrument panel will flash.
The system uses what is called an IMO (Immobiliser Signal Code) signal
to talk to the electronic engine management system, or for Diesel vehicles
the Fuel Cut-off Solenoid.
The control unit can only be re-programmed if the necessary security code
is entered, which is found on the customer vehicle information card (CAR
PASS).
NOTE : If a new immobiliser ECU is fitted to the vehicle, then the code
that is entered will be stored in the memory for any future programming
requirements.
If a different code is used to that on the CAR PASS, please ensure this is
written down and passed to the customer for safe keeping.
It is not possible to change this code once programmed.
Transponder (Mounted in key fob)
The key fob contains a small electronic circuit (Transponder) which is
powered when in close proximity to the control unit using cordless voltage
power. Each transponder has a different code for security.
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