Steering wheel controls: General
The steering wheel control consists of 3 units (7 connectors) which are mounted in the steering wheel and airbag control module. The steering wheel control provides SID with information regarding activated connectors.
The SID supplies +5V to the steering wheel controls via pin 24 and grounds them via pin 23.
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.
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 |
| 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 to activate the horn and send audio function bus information.
On cars without steering wheel controls (cars without audio system), only the steering wheel switch for the horn is used.