Originally Posted by TerraTug

A little background first: I installed aftermarket running boards with courtesy lights i wanted to activate with the key fob, doors, essentially anything that would cause the interior/cargo light to trigger. Some models are prewired for running board lights with connectors on the frame rails ready to go, some are not and i do not know for sure which models are. Ours is not. So I wired them to the gray/purple wire in the door sill labeled courtesy light and after a few days, the whole circuit shut down meaning no more interior lights, cargo lights, or running board lights. Checked the fuse and everything else I could think of which was all fine. So i did some research and this is what i found.

The courtesy lights and running boards (also sometimes noted as "puddle lights," inconsistently) run off the same fuse (15A) BUT THEN run through the BCM in 3 different channels: Puddle Lights (purple), Courtesy Lights (gray/purple), and a channel labeled as "unused". Each channel has an AMP tolerance that is monitored by the BCM. When the amps through the circuit are too high (signaling an overload or short) for too long, the BCM shuts down the channel which can only be reactivated by running a check through the OBDII port, and will permanently deactivate after a certain number of instances at which point the BCM must be replaced. Personally, i think this is kind of a crappy setup as the fuse should be oriented in a way to protect the BCM but i'm sure the current setup is cheaper and easier for FORD and still complies with whatever fire preventative/saftey regulations to which they must adhere.

One may be able to get by running some LEDs off the circuit, especially if LEDs are added to the interior and cargo lights to reduce overall current draw, but I'd avoid it all together. The puddle light is the lead from which the running boards should be run. The wire is purple (VT) and runs in the same harness as the courtesy lights through the door sills on both sides. But be careful, on certain models, there is a prewired connector under the cab just forward of the bed on the frame rails, ready to go and there is no need to tap the wire in the door sills. If you do not have this prewired connector, DO NOT CONNECT ANYTHING TO THE PURPLE WIRE RUNNING THROUGH THE WIRE BUNDLE ON THE FRAME RAIL UNDER THE CAB. It is an identical purple wire, but is twisted in a helix pattern with another wire and these together are the ABS sensor leads. Messing with them will have negative consequences. On models without the prewired connectors, the "puddle light" lead does not extend past the engine bay under the truck, it terminates in the engine bay at the harness connector.

The puddle light circuit runs the factor available illuminated running boards that have 4 wedge type bulbs. I don't know how many amps the circuit can handle before it will shut itself down but if you run 4 or less conventional bulbs of the same or less watts or a bunch of LEDs, you'll be fine using this source without overloading the circuit and shutting down the BCM.

A last word of warning, some but not most manufacturers make LED replacement bulbs for stock filament bulbs that incorporate a resistor so they draw ~ the same amps as to not throw a code for a burned out light, sometimes labeled as CAN compatible. These do NOT draw less current and should be treated like a filament bulb. They also heat up as much as filament bulbs due to the resistor.

Hope this helps someone out there avoid some serious agitation!

Originally Posted by Hedgehog1

I installed the full length led strips above the running boards a few months ago on my 2016 crew cab lariat. It had the connectors on the frame so it was easy. My buddy liked it so much he wanted them on his 2012 supercab XLT. His did not have the factory connectors so I found the correct wire for the puddle lights at the bcm in the passenger kick panel. It is located in a black 16 pin connector. This connector is one of the closest to the firewall and I believe the lowest connector also when looking at the bcm.the wire color is purple and it is pin 1 in the 16 pin connector.

Originally Posted by cursedag

Hello- I have a 2011 F250. I followed the wiring diagram in the linked docs in this post, but my vehicle BCM cables connect to the power distribution unit not the BCM unit. I have a BCM unit, but I couldn't find the correct wiring diagram from the BCM to the power unit (dont know what its called).

Can anyone offer any advice on the wiring connections between these two units?

I overloaded the BCM channel for the dome light and am replacing it. I would like to wire in a relay into the wire that powers the dimmer for all 3 channels. The relay will not run properly on the "dimmed" wire.