The PWM control in the G7 Honda is a 200Hz PWM square wave running at 10v Peak.
Dash-light control full brightness: PWM stops and Line drops to 0 volts.
Dash-light control 90% brightness: PWM around 10% on 90% off
Dash-light control 50% brightness: PWM 50% (1:1) or 50% on 50% off
Dash-light control fully dimmed: PWM around 90% on 10% off
The PWM drive line may be limited in its current sink capacity, therefore if you want to control the brightness of other lights with this signal, it would be advisable to interface this line via a small two transistor circuit.