Light Check Module (LCM): Dimmer
The LCM controls the KL 58g circuit (instrument cluster, LCD, and switch back lighting). The KL58g signal is a pulse width modulated signal which is an output of the LCM as well as a signal output over the bus line.
The dimmer input to the LCM on early models is via a potentiometer. Later models use an electronic dimmer which uses a pulse-width modulated signal to the LCM.