Passenger headlight inop but bulb and DC power present

Sounds like you're making the classic mistake of measuring the voltage without the bulb in place. Voltmeters present a very small load vs a bulb. Insert a pin in the + wire near the bulb and measure with the bulb inserted. If not OK then you have a high impediance open upstream of the bulb. If OK insert a second pin in the ground wire and if it measures 0V then the connector is bad. If it's corrosion you should be able to clean it.