Why do the backup lights on my 1995 tahoe come on when my headlights are turned on?

Make sure you have the correct bulbs in. Check for shorting at the bulb sockets. Pull the bulbs, read the bulb number and make sure it is what is called for. Any car parts place can give you the correct bulb number or there is a light chart in the light bulb section that may help. If you have a bent or damaged pin it may be sending power to your backup lights when headlight power is applied. If you turn on just the parking lights, does the back up lights come on? As we all know the headlights are up front and the back up lights are in the back. the only common connection will be through the lights to the rear that share the same socket with the backup lights.