Principle of Operation
SID UNIT IMPUTS
- +30 (pin 15)
- +15 (pin 9)
- Ground (pin 20)
- Rheostat (pin 22)
- Washer fluid level (pin 1)
- Coolant level (pin 3)
- Lamp failure (pin 4)
- ICE data (pin 8)
- TSAS data (pin 5), ACS data (pin 6)
- Outside temperature sensor (pin 19)
- Input signal pins 16 and 17
Speed
Fuel level
Odometer
Accumulated fuel consumption
Inspection of fan belt
Audio display
RDS time
Acoustic signals
Diagnostics
SID UNIT OUTPUTS
- Outside temperature sensor ground (pin 18)
- Output signals pins 16 and 17
Light intensity in cabin
Rheostat
Display lighting
INFO DISPLAY
BLACK PANEL
"Engine off" time
Outside temperature
"TOP OPEN"
Diagnostics
- Lamp failure (pin 12) (only SID 1/4)
- Washer fluid level (pin 13) (only SID 1)
POWER SUPLY AND GROUND
Power Supply
The SID unit is supplied with +30 power on pin 15 and +15 power on pin 9.
When the ignition is switched on the SID unit is fully operational.
When the ignition is switched off and the audio system is on, only the CHECK systems are inoperative.
When the ignition and audio system are switched off, only the following systems are operative.
- Time check
- Clock setting
- Acoustic signals time alarm
- Outside temperature
- Communication with other systems
When the ignition, audio system and ACC are switch off, only the following systems are operative:
- Time check
- Clock setting
- Acoustic signals
- Time alarm
When the ACC assumes parking mode, the SID unit is "woken up" via pins 16 and 17.
This is to enable the SID unit to provide an outside temperature reading.
"Engine Off" time
When the ignition is switched on, the SID unit calculates how long the engine has been switched off (max. 25.5 hours).
This information is made available to other systems via pins 16 and 17.
Ground
The SID unit is grounded via pin 20.
Grounding point G34S is located on a bracket below the right-hand A pillar behind the carpeting.
INSTRUMENT AND DISPLAY LIGHTING
The instrument lighting and the displays on the SID unit and ACC are controlled by means of the rheostat when driving at night.
When driving in the daytime, the brightness of the display is regulated by means of a light sensor in the SID unit.
Light Intensity In The Cabin
The SID unit uses the light intensity as a basis for calculating the brightness of the display lighting. "Light intensity in the cabin" is measured by the light sensor in the SID unit and the reading obtained is also made available to other systems via pins 16 and 17.
Rheostat
The rheostat output is a PWM voltage which controls the clock and pushbutton lighting in the SID unit. It is also used for calculating the brightness of the display lighting.
The SID receives the rheostat signal on pin 22 and makes it available to other systems via pins 16 and 17.
Display Lighting
Display lighting brightness is calculated on the basis of the rheostat output and the "light intensity in the cabin" reading.
The display lighting brightness reading controls the SID unit's own display.
The SID makes the display lighting brightness reading available to other systems via pins 16 and 17.
WASHER FLUID AND COOOLANT LEVEL
Washer Fluid Level
Washer fluid level is monitored by a level switch connected to pin 1 of the SID. If the fluid level drops too low, 12v is applied to pin 1 of the SID.
If the car is equipped with SID 1, pin 13 of the SID grounds pin 5 of the main instrument display panel, thus causing the warning lamp to light up (on M1995 and later cars).
If the car is equipped with SID 2/3/4, the message "COOLANT LEVEL LOW" will be displayed at the same time as an acoustic signal sounds. In addition, the SID requests (via pins 16 and 17) the main instrument display panel (pins 3 and 4) to turn on the INFO DISPL lamp.
Coolant Level
The coolant level is monitored by a level switch connected to pin 3 of the SID. If the coolant level drops too low, 12v is applied to pin 3 of the SID. If the car is equipped with SID 2/3, the message "COOLANT LEVEL LOW" will be displayed at the same time as an acoustic signal sounds.
In addition, the SID requests (via pins 16 and 17) the main instrument display panel (pins 3 and 4) to turn on the INFO DISPL lamp.
BULB FAILURE
SID is informed if a bulb fails by the ICE (brake and rear lights) and a filament monitor (front lights).
Rear Lights
In the event of a bulb failure in the rear lights, the SID (pin 8) receives a message from the ICE (pin 37).
If the car is equipped with SID 1, the "LIGHT FAILURE" lamp in the main instrument display panel will be grounded via pin 12 of the SID unit.
If the car is equipped with SID 2/3/4, either of the messages "BRAKELIGHT FAILURE" or "REAR LIGHT FAILURE".will be displayed. In addition, the SID requests (via pins 16 and 17) the main instrument display panel (pins 3 and 4) to turn on the INFO DISPL lamp.
Front Lights
In the event of a bulb failure in the front lights, pin 4 of the SID will be grounded by the filament monitor. If the car is equipped with SID 1, the "LIGHT FAILURE" indicator lamp in the main instrument display panel will be grounded via pin 12 of the SID unit.
If the car is equipped with SID 2/3/4, the message "FRONTLIGHT FAILURE" will be displayed. In addition, the SID requests (via pins 16 and 17) the main instrument display panel (pins 3 and 4) to turn on the INFO DISPL lamp.
COMMUNICATION WITH ICE
The SID unit receives the following information from the ICE:
- Rear light or brake light failure.
- An order to activate different sounds for:
direction indicators
seat-belt reminder
ignition key reminder
lights reminder (M1994 only)
Communication takes place between pin 8 of the SID and pin 37 of the ICE.
COMMUNICATION WITH THE TSAS HOOD SYSTEM
On the Saab 900 Cabriolet, the TSAS control module monitors operation of the hood. Should a fault arise, hood movement is stopped and the TSAS control module sends a pulse to pin 5 of the SID which then displays a fault message.
The Saab 900 Cabriolet incorporates the following CHECK messages.
COMMUNICATION WITH ACS
If the car is equipped with an ACS (Sensonic), the SID receives information on the system via pin 6. Communication is of single-wire data link type.
The following messages can be displayed:
- "DISENGAGE GEAR"
Displayed if input shaft speed exceeds 7000 rpm after changing gear or if neither the brake pedal nor the accelerator is depressed when the car is stationary with a gear engaged. This message is also displayed if an attempt is made to start the engine with a gear engaged or with reverse gear engaged and the brake pedal not depressed.
- "SHIFT DOWN"
Displayed if input shaft speed is less than 850 rpm after changing gear.
- "OVERHEATED CLUTCH"
Displayed when the clutch is overloaded (overheated).
CLOCK AND OUTSIDE TEMPERATURE
analogue
All three versions of the SID unit incorporate an analogue clock.
The time is set by means of two buttons below the clock, one to put it forward (+) and one to put it back (-).
digital
The digital clock in SID unit 3 is used by the trip computer for performing calculations and generating alarms.
The digital clock follows any adjustment of the analogue clock. During such adjustment, the digital clock time is shown on the SID unit display. If the battery has been disconnected the clocks must be synchronized as follows:
1 First set the analogue clock and then the digital one.
2 Press SET to synchronize them.
RDS time
The RDS (Radio Data System) is an information system which is broadcast parallel with regular FM broadcasts.
By means of RDS time, the clock can be set to the time broadcast by the radio station.
1 Press the two clock setting buttons below the analogue clock for longer than four seconds (the radio must be switched on with RDS activated).
- Adjustment of the analogue and digital clocks will now take place automatically.
- The code for RDS time is transmitted once a minute over the FM network.
- For both clocks to tell the right time, they must be synchronized.
Outside Temperature Display
Information on prevailing outside temperature is provided by all three versions. This information comes from the outside temperature sensor located behind the front spoiler below the grille.
The outside temperature sensor is grounded via pin 18 of the SID unit. The temperature signal is received by the SID unit on pin 19 and made available to other systems via pins 16 and 17.
CHECK FAN BELT
If the generator is not charging, engine temperature is too high and engine speed is in excess of 300 rpm, the SID will receive a signal from the main instrument display panel. The SID then displays the "CHECK FAN BELT" message and an acoustic signal will be heard at the same time.
In addition, the SID requests the main instrument display panel to turn on the INFO DISPL lamp.
Communication takes place via pins 16 and 17 of the SID and pins 3 and 4 of the main instrument display panel.
AUDIO DISPLAY
The SID unit has facilities for displaying audio system information (radio, cassette and CD player).
When the radio, cassette player or CD player is turned on, the appropriate information will automatically appear on the SID unit's display. If a CHECK message is activated, the audio display will be replaced by the CHECK message and an acoustic signal will sound at the same time. If audio sends text while the CHECK message is displayed, the audio text will appear for 5 seconds and the top row will be empty.
The SID communicates with the audio system via pins 16 and 17.
ACOUSTIC SIGNALS
The SID unit can produce acoustic signals for various situations. The signals are assigned priority as follows:
- Warning
- Time alarm (SID unit 3 only)
- Speed warning (SID unit 3 only)
- Reminder (warning, ignition key and seat-belt)
- Confirmation (of button depression)
- Direction indicators (TICK TACK)
The SID receives requests for acoustic signals from other systems on pin 8 (ICE) as well as on pins 16 and 17 (SI bus).
DIAGNOSTICS
The SID communicates with a ISAT Scan Tool via pins 16 and 17. Communication is two-way and consequently consists of input and output signals.
TOP OPEN
If the hood of the Saab 900 Cabriolet is lowered or already down when the ignition is switched on, a signal from the TSAS control module is applied to pin 5 of the SID. The SID then sends a "TOP OPEN" signal via pins 16 and 17 to the ACC control module.
BLACK PANEL
Pressing the BLACK PANEL button causes the instrument lighting to go out. The SID unit's display lights up only if a CHECK message is activated. The display goes out again when the message has been acknowledged by the driver, unless the BLACK PANEL button is pressed.
The SID unit will also light up for 10 seconds if a trip computer button is pressed or for 5 seconds if an audio mode is displayed.