Possible electrical problem

There are two things to look at when the head lights and the tail lights do not work, but your observation of the flash-to-pass circuit working proves one of those is okay. That is the ground wire for the head light switch. That leaves the "integration" relay. Go to the combination switch connector and look for the green wire and the red/yellow wire. Those should have twelve volts all the time. If that is missing, you will need to figure out where that integration relay is located. It is only shown as an electrical switching circuit inside a computer module or relay box.