[Wgesnerjr]

If I remember correctly, the side marker and the front signal flash in an alternating pattern, right?

If so, I would think the side marker gets its ground from the front signal bulb when it is NOT activated. Therefore is lit when parking lights/headlights are on giving power to the side marker and ground thru the Front signal bulb.

When front signal is activated, the ground goes to the front signal bulb to light it and stops at the side marker. Therefore alternating the flash. Side, Front, Side Front, etc.