Although all the tail light bulbs of my 1999 Toyota Camry v6 3.0l are good, it illuminates on the dashboard at night time when I step on the brake pedal. During the day, it is off no matter how hard I step on the brake pedal. I have no idea what causes this to happen. I really need your assistance for this. Thank you.

 

This is common issue.

Change the bulbs, clean the bulb socket and electrical terminals of any corrosion. If this does not work it could be the brake light sensor. Note the center brake light is not connected to the brake light monitoring system and no action is required here.