Mobilizing The Car: General: Function
WARNING: This page is about a different car, the 2002 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.
When the key is placed in the ignition and turned to the ON position (+15), the antenna unit receives the immobilization data which is passed on to pin 39 on the TWICE control module. The control module verifies and approves the code and passes it on to the bus. If the code is valid, the engine management system reads it from the bus. The start function block is lifted and the starter relay operates via pin 4.