Let me first say I have not had to deal with this particular system before.
Very basically, Pulse Width Modulation is in effect turning on and off a signal very quickly. The time off compared to the time on is called the duty cycle. By adjusting the duty cycle, you are adjusting the equivalent DC value (RMS value).

How does this apply to your system, you ask. I am assuming by lights you mean the dash illumination. By adjusting the duty cycle and raising or lowering the RMS value, you increase or decrease the illumination intensity. This is a very effecient way of varying the voltage. It is very common to see PWM in DC motor control for this very reason. I'm suprised Honda would make the PWM frequency in the audible range.
If this information is correct, get someone to help you determine the frequency of the PWM so you can choose an appropriate capacitor value to fix the problem.


Alex Lear