No Power to factory trailer connection for running lights (2002 Prerunner)

I have what I presume to be a factory 4 flat trailer wiring connector. Everything works except for the running light / trailer license plate light connector has no power. The problem is truck side. No power has been verified up to the wiring connector next to the spare tire so the problem has to be further up. I've checked my factory wiring diagrams and I can't see anything showing how /where the trailer connector ties into the overall electrical.

Is there a junction box or another wiring harness connector I can check to start isolating the location of the problem?

 

I've been digging through the manual and I can't find what I'm looking for. But, the thing you'll want to check is the taillight adapter box. It provides isolation between the trucks circuits and the trailers circuits, as far as I know. They don't last forever, for some reason. Mine is laying on the floor behind my drivers seat, but i think its supposed to be mounted.

 

You have a extra cab or double?

 

Yeah the stock trailer adapter/convertor box thingies are kinda known failure points unfortunately.

 

Double cab

 

If you have the OEM wiring the converter on a double cab is on the back wall behind the LH rear seat, there are 4 inline fuses on the wiring (will probably be hidden behind the carpet) take a look there.

 

Thanks brother, I'll check it out!

 

What is the deal with "OEM" trailer converter? I don't see any mention of it in any FSM. Is it a "dealer add option"? Same like the alarm?

 

Idk, I installed one myself in my 04. I would think if truck came from factory with tow package it’d have have the OEM converter.

 

there aren't a ton with them but they are common enough to have diagrams and illustrations. pretty sure they were factory installed as the wire loom is neatly done. not sure I trust a dealer to do it that well?

 

If it ends up being too much hassle to get to I'll probably just splice into the truck's running light circuit right at the license plate lights and wire it over to the trailer plug.

 

FWIW new trailer harnesses are fairly cheap and don't take that long to install.

 

Just be advised that the point of the converter is to isolate the trailer from the truck so if some thing fails you don’t loose the entire system truck and trailer.

 

I only know about it because there was a recall on my truck for it: (covers tacos and tundras)

https://www.cars.com/research/toyota-tundra-2000/recalls/

 

Wow, I thought I was going to have to rip up carpet and stuff to get to it and didn't realize all I have to do is fold the back seat down and it's literally hanging on a bracket right there in the open.

 

Yes, sorry I meant the wiring/fuses may be behind the carpet. They may also be covered in a protective foam tape.

 

Gotblika, you're spot on! So all the little fuses were conveniently marked w/ tape indicating what they were for. Mine simply had a burned inline 5A fuse and now I'm back up w/ full power. Thanks to everyone who posted!

 

For the extra cab it should be mounted in the floor compartment below the LH rear seat.