RoyAllen, just to clarify, the headlight warning buzzer used to work and doesn't now, is that correct? As opposed to something like, you got a new car and it's supposed to have a buzzer but it has never worked.
I've been poking around wiring diagrams but not having a lot of luck; nowadays so much is controlled by the ECU; it's not like the older cars where there's a physical wire between the headlight switch and the buzzer; in modern cars both wires go to the ECU, meaning you don't know whether a particular function of the ECU will cause the buzzer to go off or not.
Anyway, I found an example where a guy with a Dodge Dakota was having the same problem you are; in his case he found that there were two wires going to the door switch and one of them was no longer connected, and that resulted in the headlight warning not working any longer. Here's the forum posting.
[link|https://dodgeforum.com/forum/1st-gen-dakota-tech/207942-headlight-on-reminder-not-working.html|headlight-on reminder NOT working - DodgeForum.com|new_window=true]
As a side note, it's actually pretty easy to make a headlight warning buzzer for yourself; you just need a normally closed relay and a 12V buzzer. The ignition powers the relay coil to disconnect the buzzer when the car is turned on, and the headlight power goes to the buzzer so if the ignition is off, the hot wire to the lights runs the buzzer. Here's the Instructable showing how to make it yourself.
[link|https://www.instructables.com/Vehicle-headlight-reminder/|Vehicle Headlight Reminder - Instructables|new_window=true]
The two things I can think of to check would be the function of the door switch; does the dome light come on when you open the door? There's usually only one buzzer, so if it works for any other function like not fastening your seatbelt, then it's probably good for the headlight warning.