Brief description: General

WARNING: This page is about a different car, the 2003 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Identifying Bus Diagram

Courtesy of SAAB-SCANIA OF AMERICA, INC.

The bus is divided into a:

P-bus (Powertrain bus)
I-bus (Instrument bus)
O-bus (Optical bus).

A control module sends a message by sending ones and zeros in a predefined order. The control module only sends a message if no other control module is presently sending. The meaning of the combinations of ones and zeros is predefined so that all the control modules can interpret the information in the same way. The message contains information about what is being sent and the value, for example "Coolant temperature" 100°C or "A/C ON".

Fig 2: Identifying Bus And Components

Courtesy of SAAB-SCANIA OF AMERICA, INC.

The data link connector can access both the P-bus and the I-bus. With an adapter, Tech2 can be connected to the data link connector and can communicate with the different control modules on the P-bus and I-bus. Diagnostic communication with the control modules on the O-bus occurs via the ICM, which functions as a "gateway".

Certain information sent by a control module is made available to all other bus control modules. The CIM relays information between the I-bus and P-bus. The ICM makes sure that information available on the I-bus and P-bus is available on the O-bus, and vice versa.