GEN 2 Upfitter Switches

[smurfslayer]

If you have FORSCAN, check for a DTC, something from the BCM or similar.

I wired up my BD rear facing lights trying to get power off the bed lights because I was trying to avoid getting power from the battery. Unlike practically everyone on FRF who has done this, I don’t have constant power at the trailer plug and according to internet lore, the F150 has a smart plug that only sends power when it senses draw...? anyway, I tried grabbing power at the switch for the bed lights, and like you, it worked for a few minutes and then stopped, as well, my bed lights were dead.
I fired up the forscan tablet and found a BCM diagnostic code. Cleared it, and bed lights worked again.
i ran the battery home run in less time than it took to deal with the bed light switch.

 

[gopher870]

Great suggestion!!!! Will try right away as I have some Forscan adjusting to do from previous changes I made.

 

[FordTechOne]

If you have FORSCAN, check for a DTC, something from the BCM or similar.

I wired up my BD rear facing lights trying to get power off the bed lights because I was trying to avoid getting power from the battery. Unlike practically everyone on FRF who has done this, I don’t have constant power at the trailer plug and according to internet lore, the F150 has a smart plug that only sends power when it senses draw...? anyway, I tried grabbing power at the switch for the bed lights, and like you, it worked for a few minutes and then stopped, as well, my bed lights were dead.
I fired up the forscan tablet and found a BCM diagnostic code. Cleared it, and bed lights worked again.
i ran the battery home run in less time than it took to deal with the bed light switch.

Surprisingly, the upfitter switches do not incorporate any electronic modules. They are a very basic design; the switch operates a relay mounted in the Battery Junction Box (BJB) and the relay supplies the power to the fuse. Very straight forward. I will try and post wiring diagrams for reference.

If you have no power at the fuse, you may have a bad relay in the BJB. Try swapping them and see what the results are.

*Edit - Current generation BJB upfitter relays are integrated with the junction box and cannot be swapped*

 

[FordTechOne]

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[gopher870]

Where would I find the Battery Junction Box?

 

[FordTechOne]

Where would I find the Battery Junction Box?

Passenger side of the engine bay near the shock tower.

I just looked at the diagram again, the upfitter relays are non-servicable (integral to the BJB). So if one becomes damaged (not common), it requires BJB replacement. The positive aspect is that the newer BJBs can be replaced separately from the body harness; older models come as one assembly.

 

[smurfslayer]

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extremely helpful and useful info, thanks !

 

[gopher870]

Should I be looking for a box similar to the fuse box or something else. Google has failed me. I am unable to locate anything that could contain six relays.

I definitely found the passenger side shock tower.

 

[FordTechOne]

Should I be looking for a box similar to the fuse box or something else. Google has failed me. I am unable to locate anything that could contain six relays.

I definitely found the passenger side shock tower.

It is a fuse box. Unfortunately, the relays are non-serviceable. Meaning they're built into the BJB. If one got smoked, it requires BJB replacement.

 

[gopher870]

Thank you. I was still feeling beaten that I could not locate them. :-(