The horn sounds and hazard warning lights flash for about 27 seconds if this button is pressed for more than 0.5 second. To stop the horn and lights, press any button on the transmitter.
Blind Spot Detection Indicator Repair procedures
Removal
1.
Disconnect the negative (-) battery terminal.
2.
Remove the mirror (A) from the mirror holder.
Be careful not to damage the fixing clips (A).
3.
...
Climate Seat Unit Schematic Diagrams
Circuit Diagram
...