System Overview

System Overview, Function






System Overview, Components Connected To Bus






System Overview, Components Connected To K Lead






System Overview, Brief Description

Background
An I bus (Instrument Bus) which connects the MIU, SID, ACC and Audio system to each other has been a feature of the Saab 900 since M1994. This bus allows large volumes of information to be exchanged between the control modules using only two leads. The diagnostic tool is connected direct to the bus.

Most of the control modules in the Saab 9-5 M1998 are connected to one of these two bus systems.

P bus and I bus in the Saab 9-3
The two powertrain systems EDC 15 and the diesel pump are not connected to the I bus. These systems require much faster communication so that there are no noticeable delays, when EDC requests a new fuel mass per injection or a new injection angle.

Therefore, they are connected to a separate bus called the P bus (Powertrain Bus). Communication on the P bus is ten times faster than on the I bus.

The P bus is also connected to MIU. The MIU is responsible for making the information that is available on one of the buses also available on the other. The other powertrain systems, Trionic, Motronic and TCM, as well as the auxiliary heater for diesel engines, are not connected to the bus.

Note also that EDC 15 has a separate K lead to the diagnostic tool.

All the other bus systems communicate with the diagnostic tool via DICE, one of the I bus control modules.