ok .. just finished this and wanted to add some info from what i discovered.
First off, if your gonna try to determine which wire is ground with a multi-meter,
forget it ..
lol .. i tried and after getting a ground reading on both connections ( 3 times ) i examined the schematic and found that .. even IF you are on the 12v+ connection for the lamp, that lamp is connected to the next lamps 12v+ ** WHICH in TURN is CONNECTED TO THE GROUND ** .. so .. you'll get a ground reading on every connection unless you take out all your lamps ..
Theoretically, all the lamps could be hooked up backwards.
BUT , since this circuit we are adding "shares" a ground. We have to be sure it's actually connected in the right way.
Here are the wire colors you'll need to pay attention to.
RED/BLK is the 12v+ on the front most corner light ( the one that stays on )
That is the only wire you need to cut / splice in the corner .. i did this last.
The bumper light socket wires are BLK for ground & GRN/BLUE & GRN/Yellow for 12v+.
I connected the bright circuit for the turn signal first and tested that, then
I ran the single wire up to the corner light for the additional filament in the lamp.
Solder and heatshrink everything, properly ground it all .. your good to go ..
ALSO: i wanted to add that .. a relay could be added to each side that would turn the running light off when the blinker was activated.
This way you'd have the best of both worlds ..