2001 Honda Civic Dashboard Lights Out

It's common for people to mix up lighting wires when they replace the radio. The original radio uses two wires for the lights. There's one from the tail light circuit to tell the display to dim when you turn on the head lights. There's a different wire from the dash lights that tells the display how much to dim. Both of those wires will measure very low resistance to ground due to all the bulbs you're reading through, so they get mistakenly identified as ground wires. Hooking either of them to the radio's ground wire will create a short circuit through the radio antenna's ground and cause a fuse to blow.

Connecting the two lights wires together can cause a fuse to blow or the dash lights to not work, depending on how the car's electrical system is designed. The fact that you found two wires at the radio that affect the dash light operation proves you're working with wires that shouldn't be connected to the new radio. You could be back-feeding the dash lights from a power wire or something like that. The first thing to do is unplug the radio. If the dash lights start working properly, two wires are being connected internally inside the radio when the plug is connected. If the lights still don't work, the problem is in the wires leading up to that connector.