Brief description of TWICE: Immobilizer
WARNING: This page is about a different car, the 2001 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.
The car is fitted as standard with a system which prevents the car being started without the correct key. For this, a transponder is incorporated in the key with a unique code for that transponder.
On the ignition switch is a receiver that receives the identification code from the transponder and passes this to TWICE.
TWICE has been programmed to recognize the car's transponders and if the key in the ignition switch is correct, the car can be started.
The TWICE, MIU and engine control modules should be programmed to recognize each other. When changing one component in the immobilizer chain, the control modules must be co-programmed.