The system lets you know when a lamp is out. It detects a change in current when a lamp is out and displays the problem in your dash. For it to work properly you have to use exact OEM replacement lamps. If you use a random lamp from autozone you will still get a warning in the dash even though all lamps light up. This is because other lamps operate at different current levels than the OEM lamps so the current sensing module thinks there is still a problem.
