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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 below.

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.

Switch

Voltage (V)

Resistance (ohms)

Horn

0

0

VOL -

0.7

82

VOL +

1.2

164

SRC (select audio source)

1.8

284

SEEK >>

2.4

464

<< SEEK

3.0

794

NXT (settings for audio sources)

3.6

1474

Normal

4.2

3674





The SID unit uses the information to activate the horn and send bus information for the audio functions.

On cars without steering wheel controls (cars without audio system), only the steering wheel switch for the horn is used.

Diagnostics

If there is an open circuit/short circuit for more than 5 minutes, diagnostic trouble code B2371 is generated. Applies only to cars with Saab Audio System steering wheel controls.