System Overview

System Overview:

- SID unit, (541)
- Rheostat (16)
- Steering wheel controls (633)
- Horn switch (41)
- Horn relay (68)
- Horn (40)
- Temperature sensor, outside air (286)
- Coolant level sensor (242)
- Washer fluid level sensor (195)
- Filament monitor, front (228B)
- Parking Heater (409)

Main Components

Main Components:

Brief Description

General
The purpose of the SID unit is partly to provide the driver with information and partly to control the horn, instrument and display lighting, and perform calculations for the SID unit trip computer. 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:
- Temperature sensor, outdoor
- Steering wheel controls
- Engine coolant level sensor
- Washer fluid level sensor
- Filament monitor, front lights
- Rheostat
- Interior light sensor

Temperature sensor, outdoor
The temperature sensor sends information on the current outdoor temperature to the SID unit. The display shows the temperature in the interval -40 - +50 °C (-40 - +122 °F).

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 in the sensor. The display in cars fitted with the Saab Audio System shows the station to which the radio is tuned. When a button is pressed, the SID reads a voltage level.

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

Engine coolant level sensor
The sensor detects a low coolant level and informs the SID unit.
FILL COOLANT FLUID is displayed.

Washer fluid level sensor
The sensor detects a low washer fluid level and informs the SID unit.
WASHER FLUID LEVEL LOW is displayed

Filament monitor
The filament monitor tests the front headlamp function and passes the information to the SID unit.
FRONT LIGHT FAILURE is displayed.

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's 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 selected units and language 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:







Time
The SID unit contains a digital clock with the current time, date and month 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 outputs to the bus. (Certain markets).

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 is used to show the radio, cassette and CD settings on cars with the Saab 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 output to the bus to be used for start settings for the ACC system among others.


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:

A smaller number of control modules are connected to the bus in the Saab 9-3 compared with the Saab 9-5.

The two power-train systems, EDC and the diesel pump, are however not connected to the I-bus. These systems require considerably faster communication so that no delays are noticeable, e.g. when EDC requests a certain fuel mass for injection.

Therefore, they are connected through a separate buss called the P-bus (Powertrain Bus). The P-bus has a data transfer rate ten times higher than that of the I-bus.

The P-bus is also connected to the MIU (Main Instrument Unit). The MIU ensures that the information that is available on one bus is also available on the other.

SID uses the following information












The SID sends out the following information