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Brief description of the SID

Brief description of the SID

General

The purpose of the SID unit is firstly to provide the driver with information and secondly to control the horn, instrument and display lighting, and perform calculations for the SID unit trip computer functions. It has its own diagnostic function and diagnostic trouble codes are generated when faults occur.

The SID unit receives information from its own sensors and switches as well as from other systems. The SID unit sends out certain information on the bus.

The SID unit has the following sensors:


• Outside temperature sensor

• Steering wheel controls

• Coolant level sensor

• Washer fluid level sensor

• Filament monitor, front lights

• Rheostat

• Interior light sensor


Outside temperature sensor

The temperature sensor sends information on the current outside temperature to the SID unit.

Steering wheel controls

There are 7 control buttons on the steering wheel. One is used to activate the horn, the others to control the audio system. When a button is pressed, the SID reads a voltage level.

On cars without an audio system, only the horn button is fitted.

Coolant level sensor

The sensor detects a low coolant level and informs the SID unit.

Washer fluid level sensor

The sensor detects a low washer fluid level and informs the SID unit.

Filament monitor

The filament monitor tests the front headlamp function and passes information to the SID unit.

Rheostat

The SID unit uses the current rheostat setting to control the button and display lighting on the SID unit.

The rheostat value is output to the bus for use in adjusting the control and instrument lighting.

Interior light sensor

The light sensor is integral with the SID unit and used to measure the light intensity in the vehicle. The SID unit uses the current light reading and rheostat value to determine the intensity of the display lighting.

The interior light reading is output to the bus for use in adjusting the light intensity of the indicator lamps on the main instrument unit.

The display lighting value is output to the bus to control the light intensity of the displays.

Units and languages

The SID unit display of unit combinations and language can be selected according to the market. The following combinations are available:

Unit combinations



Language

litres/100km + °C (24 hour)



Swedish

miles/gallon (US) + °F (12 hour)



English

miles/gallon (imp) + °F (12 hour)



German

miles/gallon (imp) + °C (12 hour)



French





Italian





Spanish



The units and language selected are output to the bus for use by other systems.

Sound

The SID unit has an integral speaker for acoustic signals for its own functions and the functions of other systems.

Trip computer

The trip computer in the SID unit is operated by the buttons under the display.

The computer is available in two versions, SID 1 and SID 2 with the functions shown in the table:

Functions

SID 1

SID 2

TEMP (outside temperature)

X

X

DTE (distance on remaining fuel).

X

X

FUEL (average fuel consumption)

X

X

SPD (average speed)

X

X

DIST (distance to destination)



X

ARRIVAL (arrival time)



X

ALARM (time alarm)



X

SPD W (speed warning)



X



Time

The SID unit contains a digital clock with the current time, date and month which are always visible when the SID display is on. The year is included but not displayed.

The clock is adjusted manually but can also be adjusted by RDS time which the radio sends out on the bus.

CHECK messages

The SID unit display can be used by all connected systems to show CHECK messages.

Service message

Service reminder showing when it is time for a service.

Audio display

The SID unit display can be used to show the radio, cassette and CD settings for the car's audio system.

Horn

The SID unit activates the horn when information has been received from the steering wheel control.

Night Panel

The Night Panel function switches off the display and parts of the instrument lighting, and dims the button lighting.

The Night Panel information is output to the bus for use by other systems.

Engine off time

The SID unit calculates the length of time the engine has been switched off. This time information is used by the outside temperature function.

The time value is output to the bus to be used for the starting settings for the ACC, etc.

Important

The Service Manual does not cover the complete operation of the SID unit. More detailed information is given in the Owner's Manual.


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 ten times higher than that of the I-bus.

All information sent out on a bus 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.