that part is not needed , the way i done it was cut the ground wire to the side marker light and route it to the signal wire in the front grill , when the signal is turn on power goes to the side marker light and all the lights on the brown wire serves as a ground and will flash, when the lights are on the bulbs on that side serves as a ground and the side marker light will blink on and off the power is sent to both sides of the bulb making the bulb go off , that how i got wired on my pinto , only on the front , if you do the back the side marker light wil go off when you hit the breaks,