Bus communication
| Bus communication |
| P-bus and I-bus |
All the control modules in the Saab 9-5 are connected to the bus except those for the ABS and SRS.
The bus is divided into a Powertrain bus (P-bus) and an Instrument bus (I-bus).
The data transfer rate on the P-bus is ten times faster than on the I-bus.
All the information sent from one control module is accessible for all other control modules on the bus. The MIU is responsible for ensuring that information available on one bus is also available on the other bus.
The control modules send information to the bus at regular intervals. The time between two transmissions depends on what information is being sent and varies between 10 milliseconds (0.010 seconds) and one second. The control module also sends information every time the information changes.
Information is transmitted between control modules on two leads, BUS+ (green lead) and BUS- (white lead). Both P-bus leads are twisted to reduce their sensitivity to electrical interference.
On MIU connected to both the I-bus and the P-bus, the twisted leads are connected to the following pins of the 12-pin connector:
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I-bus:
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Pin 5 (green lead Bus+) Pin 12 (white lead Bus-)
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P-bus
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Pin 4 (green lead Bus+) Pin 11 (white lead Bus-)
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| Diagnosis |
In a bus system, all the units must be able to communicate with each other. For example, the engine cannot be started if Trionic is unable to receive immobilizer information from TWICE.
Permanent bus faults
All communication between Tech 2 and the bus-connected systems goes via DICE. Irrespective of which system is being contacted, Tech 2 and DICE will check to see that all the bus-connected systems in the car are activated and communicating. If any bus-connected control module is missing, Tech 2 will detect this. This means that all the bus-connected control modules are communicating correctly if there is no warning from Tech 2.Intermittent bus faults
Trionic and TCM check to see that all the control modules they receive information from are communicating correctly. In the event of an intermittent fault occurring in bus communication, a diagnostic trouble code will be set in Trionic and TCM. The cause of the fault could be that the power supply or one of the bus leads to the control module in question is absent.Incorrect values on the bus
Diagnostic trouble codes are set in Trionic and TCM if any information they receive from the bus has an incorrect value. The trouble code readout will refer to the faulty system.For further information about the bus, see Diagnostics communication .
| DICE communication, lighting: |
| Information | Sensor system | |
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Position lights
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DICE
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Position lights, unit ON/OFF. Information used by SID.
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Rear Fog Light Out Of Action
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DICE
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Rear Fog Light Out Of Action, unit YES/NO. Information used by SID.
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LH direction indicators
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DICE
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LH direction indicators, unit ON/OFF. Information used by MIU and SID.
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RH direction indicators
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DICE
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RH direction indicators, unit ON/OFF. Information used by MIU and SID.
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Rear fog light
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DICE
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Rear fog light, unit ON/OFF. Information used by MIU.
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Reverse gear
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DICE
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Reverse gear, unit ON/OFF. Information used by PMM.
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Acoustic
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DICE
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Acoustic information. Used by SID.
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+54
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DICE
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Ignition +54, unit ON/OFF. Used by TWICE.
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| TWICE communication, lighting: |
| Information | Sensor system | |
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LH Rear Light Out Of Action
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TWICE
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LH Rear Light Out Of Action, unit YES/NO. Information used by SID.
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RH Rear Light Out Of Action
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TWICE
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RH Rear Light Out Of Action, unit YES/NO. Information used by SID.
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LH rear light
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TWICE
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LH rear light, unit ON/OFF. Information used by DICE.
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RH rear light
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TWICE
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RH rear light, unit ON/OFF. Information used by DICE.
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LH Brake Light Out Of Action
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TWICE
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LH Brake Light Out Of Action, unit YES/NO. Information used by SID.
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RH Brake Light Out Of Action
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TWICE
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RH Brake Light Out Of Action, unit YES/NO. Information used by SID.
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High-Level Brake Light Out Of Action
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TWICE
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High-Level Brake Light Out Of Action, unit YES/NO. Information used by SID.
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Brake lights
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TWICE
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Brake Lights, unit ON/OFF. Information used by Trionic, TCM and SID.
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Acoustic
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TWICE
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Acoustic information. Used by SID.
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Driver's Door
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TWICE
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Driver's Door, unit OPEN/CLOSED. Information used by MIU, DMM, PSM and DICE.
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Passenger Door
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TWICE
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Passenger Door, unit OPEN/CLOSED. Information used by MIU, DMM, PSM and DICE.
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LH Rear Door
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TWICE
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LH Rear Door, unit OPEN/CLOSED. Information used by MIU and DICE.
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RH Rear Door
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TWICE
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RH Rear Door, unit OPEN/CLOSED. Information used by MIU and DICE.
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Boot Lid
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TWICE
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Boot Lid, unit OPEN/CLOSED. Information used by MIU and DICE.
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Test Brake Lights
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TWICE
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Test Brake Lights, unit ON/OFF. Information used by SID.
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Hazard flashers
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TWICE
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Hazard Flashers, unit ON/OFF. Information used by DICE.
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| SID communication, lighting: |
| Information | Sensor system | |
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Rheostat Night Panel
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SID
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Rheostat Night Panel, unit %. Information used by Audio, ACC, DICE and MIU.
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Rheostat level
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SID
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Rheostat level, unit %. Information used by Audio, ACC, DICE and MIU.
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Night Panel
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SID
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Night Panel, unit ON/OFF. Information used by Audio, ACC, DICE and MIU.
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