How / Where can I interface with the D4V2's button circuit?

I’m thinking of implementing an automatic headlight system using a small arduino nano and a light sensor. When light from the sensor reaches a specified threshold, it will briefly send 2 sequential 5v signals to toggle high-beam mode on the light.

I’m pretty ignorant in the light’s design and PCB layout. Where can I find the button terminals on the PCB for the D4v2? Will a 5v signal to the button switch work or does it need to be stepped down for the battery in any way?

The button shorts a pin to ground, the leads are soldered to a pad marked ”S” that goes to this pin, and another marked ”C” which is GND. If you want to simulate a button press then you can use a small NFET to short S to GND.