9-3 Coupe (9400) L4-2.0L Turbo (B204) (1999)
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Ground connection
The SID unit is grounded via pin 1 at grounding point G34S.
Diagnostics
If there is no ground connection, the display will not be active and diagnostic communication will not be possible.
The SID unit will not generate a diagnostic trouble code if there is no ground connection.
Steering Wheel Controls
Steering Wheel Controls
The steering wheel controls consist of 3 units (7 switches) mounted in the steering wheel and airbag module. The steering wheel controls give the SID
unit information on which contacts are activated.
The SID unit supplies the steering wheel controls with +5 V via pin 18 and grounds them through pin 3.
The 7 steering wheel switches consist of 7 resistors connected in series. When a button is pressed, the switch concerned is grounded, see table.
Depending on which button is pressed, the aggregate resistance in the circuit varies and with it the voltage detected by the SID unit.
The horn switch (41) is connected in parallel with the steering wheel switches and when it is pressed, pin 18 is grounded direct to pin 3.
The table shows the correlation between the voltage on pin 18 and the switch that is activated.