Display lighting
WARNING: This page is about a different car, the 2001 Saab 9-5. However, it is still accessible from the selected car via links, so may be relevant.
The SID calculates a suitable value for the odometer display lighting using the rheostat value and the value for cabin light intensity from the light sensor.
When it is dark, the lighting is controlled by the rheostat value and when the light in the cabin increases, it is controlled by the value of the light intensity in the cabin. This ensures that the odometer display will be easy to read in all lighting conditions.
The SID transmits this calculated value on the bus as Display lighting level, unit %.
The main instrument unit control module uses the value to control the odometer display lighting.