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 the other control modules on the bus. The MIU ensures that the information which is available on one bus is also available to the other bus.
The control modules send information to the bus at regular intervals. The time between two transmissions depends on which information is being sent and varies between 10 milliseconds (0.010 seconds) and one second. The control module also sends information every time it 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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| Diagnostics |
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 the diagnostic tool and the bus-connected systems goes via DICE. Irrespective of which system is being contacted, the diagnostic tool 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, the diagnostic tool will detect this. This means that all the bus-connected control modules are communicating correctly if there is no warning from the diagnostic tool.Intermittent bus faults
Trionic and TCM check continuously 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 on the bus, see Diagnostics and bus communication
| The MIU uses the following information: |
| Information | From | The value depends on the following sensor input, signal or function |
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LH direction indicators
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DICE
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Direction indicators LH, unit ON/OFF. MIU lights indicator lamp for LH direction indicators.
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RH direction indicators
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DICE
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Direction indicators RH, unit ON/OFF. MIU lights indicator lamp for RH direction indicators.
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Rear fog light
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DICE
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Rear fog light, unit ON/OFF. MIU lights indicator lamp for rear fog light.
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Driver's door
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TWICE
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Driver's door, unit OPEN/CLOSED. MIU lights symbol for open driver's door.
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Passenger's door
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TWICE
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Passenger's door, unit OPEN/CLOSED. MIU lights symbol for open passenger's door.
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LH rear door
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TWICE
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Rear door LH, unit OPEN/CLOSED. MIU lights symbol for open LH rear door.
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RH rear door
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TWICE
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Rear door RH, unit OPEN/CLOSED. MIU lights symbol for open RH rear door.
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Boot lid
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TWICE
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Tailgate, unit OPEN/CLOSED. MIU lights symbol for tailgate.
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Info Disp Lamp
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SID
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Info Disp Lamp, unit ON/OFF. MIU lights indicator lamp for Info Display.
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Rheostat value
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SID
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Rheostat value, unit %.
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Night Panel
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SID
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Night Panel, unit ON/OFF. MIU turns off certain instrument and display lighting.
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Display lighting
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SID
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Display lighting, unit %. The MIU uses the information to control the display lighting.
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Light intensity in cabin
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SID
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Brightness in cabin, unit Lux. The MIU uses the value to control the light intensity of the indicator lamps.
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| Information | From | The value depends on the following sensor input, signal or function |
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CHECK ENGINE Lamp
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Trionic
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CHECK ENGINE lamp, unit ON/OFF. MIU lights CHECK ENGINE lamp.
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CRUISE Lamp
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Trionic
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CRUISE lamp, unit ON/OFF. MIU lights CRUISE lamp.
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SHIFT UP lamp
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Trionic
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SHIFT UP lamp, unit ON/OFF. MIU lights SHIFT UP lamp.
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Fuel Consumed Since Start
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Trionic
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Fuel Consumed Since Start, unit 0-65535 ml. Used by SID for trip computer, can be adjusted with offset in MIU.
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Engine speed
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Trionic
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Engine speed, unit 0-7000 rpm. The MIU controls the tachometer.
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Coolant temperature
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Trionic
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Coolant temperature, unit -40-215°C. The MIU controls the coolant temperature sensor.
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Selector lever position
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TCM
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Selector lever position, unit P, R, N, D, 3, 2, 1. The MIU lights the corresponding indicator lamp.
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CHECK GEARBOX Lamp
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TCM
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CHECK GEARBOX lamp, unit ON/OFF. The MIU lights the CHECK GEARBOX lamp.
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SPORT Lamp
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TCM
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SPORT lamp, unit ON/OFF. The MIU lights the SPORT lamp.
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WINTER Lamp
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TCM
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WINTER lamp, unit ON/OFF. The MIU lights the WINTER lamp.
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Diagnostics communication
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DICE/Diagnostic tool.
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| The MIU sends the following information: |
| Information | Used by | The value depends on the following sensor input, signal or function |
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Vehicle speed
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Trionic
DICE, SID, ACC, Audio, TWICE |
Vehicle speed, unit km/h (mph).
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Acoustic warning
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SID
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Request for acoustic signal when central warning lamp or Info Displ goes on.
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Fuel level
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SID
Trionic |
Fuel level, unit litres.
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Odometer reading
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SID
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Odometer reading, unit km (miles).
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Diagnostics communication
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DICE/Diagnostic tool.
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