Are you describing the LED array used as DRL illumination as "...during the day....both headlights were on"?
The change from DRL to headlights is based on the light sensor on the dash center. That appears to be OK as the change happens when you pull into your relatively darker garage.
I'd be looking at the wiring continuity in the path "F11DL".

That is the portion of the suspect left headlight bulb circuit that is not also part of the working left DRL circuit.

 

Thanks for the info...greatly appreciated!

Interesting! Didn't realize that was what that sensor on the dash center was for. Yeah, that does appear to be functioning...the passenger side headlight is on when I pull into the garage, but driver's side light goes out. I had not noticed that there might be a change in the light color/quality.

I did not realize that DRL might be a different "bulb", or that is was otherwise separate from headlight used in the dark. Learning a bunch of stuff here.

I'll take a closer look at all of that.

Thanks again

 

I just realized that you should also confirm the integrity of the left side ground point called "G101". A less-than-sufficient ground contact having a higher than intended resistance (loose, rusty, etc.) might be 'good enough' to carry the low amperage of the DRL diodes, but might not pass enough amperage of the higher current draw headlight filament.
Unplug the "X110" connector at the left headlight.
Use an ohm meter to measure resistance from the X110 socket 5 to a known good ground (battery- charge post on strut tower, or the braided ground cable on the 'Voltec' unit right at that left headlight). There should be no measurable resistance.

and since you have the meter handy:
Leave the X110 unplugged, change the meter to a DC voltage setting, manually turn on the headlights. Measure the voltage difference between X110 socket 1 and the ground point. There should be 12-ish volts difference.
If those two are as expected, then the connection between the bulb blades and the respective X110-1 and X110-5 sockets need to be reviewed.

 

Thank you. I'll get on that.

 

Hey Lug Nut, Thank you! Turned out it was the connector itself. The terminal for the common/ground was corroded. Once that was taken care of, the headlight is functioning again the way it is supposed to. Thanks for the guidance!