Shift Illumination Circuit: Description
WARNING: This page is about a different car, the 2008 Lexus IS F. However, it is still accessible from the selected car via links, so may be relevant.
The shift illumination is controlled by the main body ECU LH based on various signals received through BEAN communication.
The main body ECU LH includes a MOS-FET (Metal Oxide Semiconductor - Field Effect Transistor) circuit that fades the shift illumination in and out by duty control.
This MOS-FET circuit has an overheat protection function as a fail-safe. If the main body ECU LH becomes excessively hot, the shift illumination turns off and remains off.
Normal operation will resume when the conditions required to turn on the shift illumination are met again.