Brightness control (rheostat function)
This switch can be used to adjust the instrument illumination. ICM controls the cabin lighting after allowing not only for the rheostat control but also for the light sensor on SID that measures the backlight. The switch provides ICM with information on the driver's chosen instrument illumination setting. A PWM signal from SIDC pin 4 to ICM pin 14 indicates the button (+/-) being pressed. The signal is 5V 960Hz PWM with pulse ratio 40% for the up button (+) and 60% for the down button (-).