Bus Communication

- Trionic T7 control module (600)
- TCM control module (502)
- MIU control module (540)
- DICE control module (628)
- Data link connector (445)
- SID control module (541)
- Audio control module (353)
- ACC control module (216)
- PSM control module (357)
- TWICE control module (632)
- PMM control module (611)
- ABS (547), TC/ABS (382) control modules
- Airbag control module (331)

P Bus And I Bus





In the Saab 9-5, all the car's control modules are connected to buses with the exception of the ABS and SRS control modules.

The buses are divided into the Powertrain bus (P bus) and the Instrument bus (I bus). Both buses are connected to the main instrument unit (MIU). The buses are electrically isolated from each other.

The P bus has a data transfer rate 10 times higher than that of the I bus.

All information sent out by a control module is available to all other control modules connected to the bus. The MIU ensures that the information which is available on one bus is also available on the other.

The control module sends out information on the bus at regular intervals. The time between two transmissions depends on which information is being transmitted and varies between 10 milliseconds (0.010 seconds)and one second. Information is also sent out by the control module whenever the information changes.

The transfer of information between the control modules takes place on two leads, BUS+ (green lead) and BUS- (white lead). The two leads are twisted to make them less sensitive to electrical interference

Diagnostics
In a bus system, all units must be able to communicate with each other. For example, the engine cannot be started unless the Trionic T7 can receive the immobilization information sent out by TWICE.

Permanent bus faults
All communication between the diagnostic tool and systems connected to the bus takes place through DICE. Irrespective of which system is contacted, the diagnostic tool first checks by means of DICE that all on-board systems connected to the bus are turned on and in communication. If any control module connected to the bus is missing, the diagnostic tool will show this. This means that all control modules connected to the bus can communicate properly unless the diagnostic tool warns otherwise.

Intermittent bus faults
Trionic continuously checks that TCM and MIU are communicating correctly. Diagnostic trouble codes will be generated if intermittent fault should occur. The cause of such faults may be that the control module has lost its power supply or one of the bus leads.

Missing control module DTC
TCM P1923
MIU P1908

The Trionic T7 uses the following information:





The Trionic T7 sends out the following information: