On my 03 Avalanche one of my back up lights stopped working. So i bought new bulbs. The old bulbs didnt look blown so i tried them in the tail lights and they worked. I checked all the fuses and they were good. Also when i changed the bulbs i changed both sides and now neither one will work. Some how i did get them both to come back on for a little while when i was testing the socket with a test light. Some one told me to look at the circuit board but i really dont know what do with it. Why do we even have a circuit board? How do i tell if the board is bad andhow bad is it to change out? If anyone knows anything about this please help. Thanks.