P-bus and I-bus
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.
In the Saab 9-3, fewer control modules are connected to a bus system compared to the Saab 9-5.
The two bus systems are I-bus (Instrument bus) and P-bus (Powertrain bus).
Both buses are connected to the main instrument unit (MIU). The buses are electrically isolated from each other.
The P-bus has a communication speed ten times faster than that of the I-bus.
All information sent out by a control module is available to all control modules connected to a bus. The MIU is responsible for making sure that information available on one bus also is available on the other bus.