Illumination level (for the gauge illumination) indication (press No. 4 button)
WARNING: This page is about a different car, the 2011 Honda Insight and 2010 Honda Insight. However, it is still accessible from the selected car via links, so may be relevant.
This diagnostic screen checks the gauge illumination input.
With the headlights on, you should see a values between 1 (max low) and 22 (max high).
When you dim and brighten the gauge with the dimmer knob, you should see this value change accordingly.