Brief description of the main instrument unit
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Brief description of the main instrument unit
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The main instrument unit conveys information to the driver and functions as an information link between the P bus and the I bus.
In the Saab 9-5, all the car's control modules are bus-connected apart from ABS. On cars with Traction Control, the TC/ABS control module is bus-connected and on cars with ESP, the ESP control module is bus-connected.
The vehicle speed is important information for many control modules. The left rear wheel sensor is used by ABS, TC/ABS or ESP for information on the wheel speed. As ABS is not bus-connected, the wheel speed signal is transferred via its own lead from the ABS to the MIU. The MIU processes the wheel speed information into the vehicle speed and sends out this information on the buses. On cars with Traction Control or ESP, the MIU receives the wheel speed information from the TC/ABS or ESP control module via the P-bus.
The main instrument unit has its own diagnostics function and sets a diagnostic trouble code when a fault occurs.
The main instrument unit incorporates the following:
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Coolant temperature gauge
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Instrument and display lighting
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Warning and indicator lamps
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The main instrument unit receives information from its own sensors and also from other systems. The control module processes the information, which is used to control instruments and lamps. Certain information is put on the bus.
The car is fitted with an electronic speedometer which shows the current speed. Information on the speed is taken from the ABS, TC/ABS or ESP control module. The left rear wheel sensor sends the speed information to the ABS, TC/ABS or ESP control module.
The main instrument unit's control module stores the distance covered and shows the mileage on the odometer display. The odometer display has a six-digit counter which the control unit continuously updates from 000000 to 999999 km (or miles). The tripmeter has a four-digit counter which starts at 000.0 and goes up to 999.9 km (or miles).
The tachometer is electronic and shows the current engine speed. The tachometer continuously receives bus information on the engine speed from the engine control module. The tachometer display in the range below 1100 rpm is damped to give a more stable display.
The fuel gauge gives the driver information on how much fuel is left in the tank. It consists of a fuel gauge in the main instrument unit and a level sensor in the tank.
When the fuel level is below 10 litres, the main instrument control module switches to fuel consumption monitoring. The information comes on the bus from the engine control module. This gives a more accurate display of the fuel level. The Fuel Reserve indicator lights when the fuel level is below 10 litres.
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Coolant temperature gauge
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The coolant temperature gauge gives the driver information on the engine coolant temperature. The information comes on the bus from the engine control module.
The car is fitted with an electronic boost gauge which gives information on the engine load. Trionic receives information on the current air mass/consumption from the air mass meter located between the air filter and the turbo intake side. The main instrument display panel receives information on the bus from Trionic.
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Warning and indicator lamps
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The main instrument unit contains the following lamps:
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Indicator lamp INFO DISPL, lights up when a message is shown on the SID unit.
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Central warning lamp, lights up when a fault occurs in a system relating to vehicle safety.
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Oil pressure warning lamp, warns the driver when engine oil pressure is too low.
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Charge warning lamp, indicates to the driver whether or not the generator is charging.
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AIRBAG warning lamp, warns the driver when a fault has occurred in the airbag system.
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Brake fluid warning lamp, warns the driver if the level of the fluid in the reservoir is too low or if a fault has occurred in the ABS system.
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Handbrake warning lamp, tells the driver that the handbrake is on.
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TCS/ESP indicator lamp, comes on when TCS/ESP is active; found on cars with TCS and ESP.
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TCS/ESP OFF indicator lamp, comes on when TCS/ESP is disengaged or on a fault in the system; found on cars with TCS and ESP.
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ABS warning lamp, lights up when there is a fault in the ABS system.
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Xenon lamp indicator lamp, lights on a fault in the automatic headlamp adjustment system, found on cars with xenon lights.
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SPORT indicator lamp, on cars with automatic transmission indicates to the driver that the SPORT mode is active.
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WINTER indicator lamp, on cars with automatic transmission indicates to the driver that the WINTER mode is active.
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CHECK GEARBOX indicator lamp, warns the driver when there is a fault in the automatic transmission.
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Fuel reserve indicator lamp, the lamp lights up when the fuel level is below 10 litres.
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CHECK ENGINE indicator lamp, warns the driver that there is a fault in the engine management system.
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Direction indicator repeater lamps, right and left. Show when the direction indicators are on.
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CRUISE indicator lamp, on cars with cruise control the lamp lights up when cruise control is engaged.
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SHIFT UP indicator lamp, lights up when a higher gear should be engaged (certain markets).
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Lights-on indicator lamp, indicates that the headlamps are on.
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Rear fog light indicator lamp, indicates that the rear fog light is on.
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Main beam indicator lamp, indicates that the main beam is on.
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Selector lever position indicator, indicates the selected gear position on cars with automatic transmission.
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Door indication, indicates if any of the doors or the tailgate is open.
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Glow plug indicator lamp. Comes on when the glow plugs are connected on cars with diesel engines.
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Instrument and display lighting
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The main instrument unit's control module controls the instrument and display lighting according to the light intensity in the cabin in combination with the selected rheostat setting. This gives a good level of lighting for day or night driving and optimum bulb life.
