You will see that pin 2 of BOTH headlight connectors is GROUND.
Pin 3 is the 12v for the low beams, pin 4 is for the high beams.
With both lights unplugged, measure the harness pins with the lights turned on.
You should see 12v from 3 to 2 for low beams, and 4 to 2 for high beams.
( If high beams are selected, you see both of the above )

If you see the 12v, then the problem is in the headlight unit(s), if not, then wiring, fuses or the Lighting Control Module ( the headlight switch )