Great idea. Would love to perform mod also. Any pics you could supply to educate would be appreciated.
I will try to detail as much as I can on here. First, there are 2 wires (a positive and a negative) coming into the engine bay that are controlled by the Aux 1 Exterior switch installed in every Grenadier. You do not have to have the extra battery or second row of switches. See pic. The wire is on the drivers side for USA spec trucks tucked just under the fender with some white plastic caps on them. They are easy to find, not covered with tape or anything.
Partial Grill removal:
You need to remove the black headlight surrounds held in by 4 torx bolts on each side
Next you will need to unbolt several torx bolts that are located behind those headlight surrounds. This will let you carefully pull out the painted upper portion of the front fender. Do this on both sides.
Next, you will need to remove the rubber trim from the top of the center grill piece. There are little black clips that hold the rubber to the top of the grill. Pry them out with a forked plastic pry tool and try to keep them together. See pic.
Once you get the bots all removed there will still be two torx bolts that are below the bumper line. I left those in and was able to pull the grill forward enough to access the lights. The lights have connectors that you can unconnect and pull out to each side of the grill so you can work on them easily.
Cut the wires about 3-4 inches back from the plug and cap off and secure the cut wire and hide it back behind the grill.
Edit: The plugs that you cut have 2 wires attached. One is striped and is positive, the other is black and negative.
Now get yourself some red and black wire about 5-6 feet long and put it in some wire loom.
I used heat shrink butt connectors to wire the plug to the wires in the loom.
The plug side wires are striped color for positive and black for negative on both plugs. Wire up the first plug on the right side (passenger in USA), then run the loom under the front grill (hidden) and over to the left side. Cut your loom wires and wire the striped plug wire to the red, and the black to the black.Now the lights are connected and positive goes to positive and negative to negative.
You can use one butt connector per positive and negative here on the 2nd light. Insert the red coming from the 1st light, and the striped coming from the 2nd connector into one side, and connect the red out the remaining side of the butt connector. So, you will have 2 wires crimped on one side of the butt connector, and one wire out the other side. Then do this for the ground, same way.
Lead the wire loom up keeping it hidden and zip tie it along the side of the engine bay existing wiring.
You can then connect the positive to the striped lead you found earlier, and the ground to the black lead you found earlier.
Test your connection by turning on the Aux 1 switch, and the lights should come on.
Note: When the truck is turned off and the switch is on, the lights will turn off. However, if you turn on the battery switch next to Aux 1 it will enable the lights to work when the truck is off. The battery switch will also turn on and off the rear load space 12 volt and the usb for the back seat passengers when the truck is off. Great feature!
Now reverse the assembly and put it back together making sure to be careful with the painted upper fender pieces that clip into place.
I hope this helps.