Headlight Wiring Diagram

General heads up on these as well:

The "Ctrl Mod" circuits are not actually intended to power lights. They're just control signals for the headlight ballast. The actual power comes from a dedicated power circuit (Pin 8).

You can probably use those Ctrl Mod circuits to trigger a relay to turn on/off accessory lights, but don't use them to actually power those accessory lights, you'll need to run a dedicated wire for power. Otherwise, your Body Control Module is going to freak out and start throwing trouble codes. (Worst case you might blow the BCM itself and require a new one.)

That’s interesting as both IAG and AVS both have you tapping into the Ctrl Mod wires. Now, IAG has you add a fuse tap, but AVS tells you to directly wire using Ctrl Mod wires and no add a fuse for power. I will have to try to figure out how I would add a fuse tap to power it. I did test after I installed and haven’t had an issue yet, but I only just installed it today and haven’t used it much.

MetroDriver25

That’s interesting as both IAG and AVS both have you tapping into the Ctrl Mod wires. Now, IAG has you add a fuse tap, but AVS tells you to directly wire using Ctrl Mod wires and no add a fuse for power. I will have to try to figure out how I would add a fuse tap to power it. I did test after I installed and haven’t had an issue yet, but I only just installed it today and haven’t used it much.

It's confusing because sometimes the BCM does actually power the circuits (such as with the taillights), and sometimes it's literally just outputting control signals. Thinking about it logically, I would guess the 18 gauge pins are actually powering something, while the 20-22 gauge are just signals. But I am not confident about that at all, and you can't easily measure it—the BCM has detection circuits that cut output and throw codes if it detects something is wrong.

Either way, all of those Ctrl Mod wires are coming from the BCM, and frankly BCM (and headlights) are expensive to replace. So it's a "tread carefully" situation.

I know @4x4TruckLEDs.com avoids the headlights altogether because of the issues I mentioned. Mabett used to sell a relay adapter harness, but it was discontinued some time ago. Not sure if anyone else sells anything similar nowadays.