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Steering wheel controls

Steering wheel controls





General

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 +5V via pin 22 and grounds them via pin 9.

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 total resistance in the circuit changes and the voltage detected by the SID unit consequently varies.

The horn switch (41) is connected in parallel with the steering wheel switches and when it is pressed, pin 22 is grounded direct to pin 9.

The table shows the correlation between the voltage on pin 22 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

In the event of a break/short to B+ or short-circuit to ground for more than 5 minutes, diagnostic trouble code B2371 will be generated. This applies only to cars with the Saab Audio System having steering wheel controls.