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Steering wheel control, Sentronic

Steering wheel control, Sentronic



General

The steering wheel controls consist of 3 units (9 switches) integrated in the steering wheel and airbag module. The steering wheel controls provide the with SID information as to which of the switches is activated.

The SID supplies +5V to the steering wheel controls via pin 24 and grounds them via pin 23.

The 9 steering wheel switches consist of 9 resistors connected in series. When a button is pressed, the relevant switch is grounded; see table below.

When a connector is pressed, the total resistance in the circuit changes, as does the voltage value which SID then reads.

The horn switch (41) is connected in parallel with the steering wheel switches. When it is pressed, pin 24 is grounded directly to pin 23.

The table shows the correlation between the voltage on pin 24 and the switch that is activated.

Switch

Voltage (V)

Resistance (Ohms)

Horn

0

0

Shift gear up (+)

0.4

44

Shift gear down (-)

0.8

95

VOL -

1.2

160

VOL +

1.7

242

SRC (select audio source)

2.1

347

SEEK >>

2.5

494

<< SEEK

2.9

709

NXT (settings for audio sources)

3.3

1041

Normal

4.0

2511





SID uses the information from the steering wheel control to activate the horn, provide TCM information on upshifts/downshifts and to send bus information for audio functions.

For additional information on controlling the automatic gearbox using the steering wheel controls, see Sentronic .

Diagnosis

In the event of an open/short-circuit to B+ or a short-circuit to ground for more than 5 min, DTC B2371 is generated.