2. Immobilizer, cars with Trionic T7 engine management system: Notes
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.
When the ignition is turned on, the TWICE checks that the right key is inserted in the ignition switch. A circuit built into the remote control part of the key sends a code by means of inductance to a coil round the ignition switch under the center console. The code is passed on to the control module, which checks that it is correct. The TWICE also checks that the right MIU is fitted in the car. The MIU continuously sends out an ID number on the bus.
If the key and the MIU ID number are OK, TWICE will send an "Immobilizer OFF" message on the bus. The Trionic T7 acts on this information by cancelling fuel shut-off, which is always activated whenever the ignition is turned on.