You would need wiring diagram for it, then simply use a test light to test hot wire when on. If not juice, bypass it with jumper wires to see if lights come on. You can also use an ohmmeter to get an idea if it is out but need specs for resistance.
Probably a bad headlight switch. Also may be the power feed wire for the headlight switch. Check both.
check the headlight/multifunction switch
check your headlight switch
Check the back of the headlight switch. They had a problem with the electrical plug to the switch melting down due to high resistance (poor connections).
possible multifunction switch, check your headlight bulbs first
Check fuse Check operation of door switches Check operation of headlight switch
check the fuse panel for blown fuse/check headlight switch
Check the bulbs and then the multifunction switch (headlight switch)
check your fuses
Check your headlight switch. Sometimes the switch goes bad and the dash lights won't light. Replace the switch for the fix.
Use a wire tester and check everything from the light switch to the headlight assembly. If there's no voltage at te headlight switch, then trace it all the way to the battery.
Check the headlight switch, if not it's probably a fusible link in the headlight circuit.