If you peruse this Diagram…
...You’ll notice there are (3) Distinct Grounds servicing this very complex Head Lamp Wiring, Fusing and Relay System:
(1) G107
(2) G103
(3) G108
These are three
distinct contact points either between the Body or the Engine that share many other electrical components that can also have an affect upon each other… especially if ANY of the Three Grounds suffer from Poor Connections, Rust or Galvanic Corrosion.
These artifacts can Increase Resistance and invite Electrical Arcing and/or Create Excess Heat and Loss of Continuity on the Wiring to each of the High and Low Beam Headlights.
Suggest that you visit THIS Link to
@Realism ‘s indelible contribution to GMT Nation with his collection and posting of the locations of ALL the GMT360 Ground and Bonding Strap Locations.
Use these Images to Locate, Unfasten, Clean Them ALL Down To Bare Metal,
then Apply a Small Dollop of Dielectric Grease to discourage Galvanic Corrosion and Re-Attach them to restore "The Goodness" of ALL of these Grounds.
https://gmtnation.com/forums/threads/electrical-ground-locations.15491/