where is hidden Fuse box location

I have a Tacoma 2003 extra cab V6 with factory installed towing wiring. Worked on one trailer with all lights working. Then I hooked up trailer #2 and lights suddenly stopped working. Circuit testing shows power only going to brown wire on 4 way flat connector and Converter. Interior and under the hood fuses are good. There is no black box behind back seat on drivers side. Got under my truck and traced trailer wires. There is a wire bundle going into the cab under the drivers seat. Doesn't seem logical. Anyone else have this? Any other location I should look?

 

Trailer lights often splice in behind the tail lights

 

Thank you 1blink. I’ve read that aftermarket wiring does that. I don’t see any wiring going towards lights but I’ll check again

 

You don't have a little box attached to the back wall of the cab a bit below the rear window? I have the factory trailer wiring and frame mounted receiver under the bumper. I bought it from the Toyota in 2004 and installed it myself with the directions provided. The conversion from 5 wire to 4 wire is handled by that Toyota box that on the single cabs is mounted on the reinforcement crossbar just a little below the top of the seat backs. Perhaps it was located in a different place on extended cab trucks?

 

Pull the door scuff plate (four screws) and peek under the carpet and see what's under there. There is for sure a harness connection there, so maybe whoever installed the trailer kit thought it would be suitable location for the trailer controller.

 

To: notrouble: I have no black box. And yes, it must be hidden elsewhere. I think I'm going to abandon this hide-and-seek game and purchase an after market harness. ie:

Hopkins Towing Solutions Trailer Wiring Harness - 43315

 

To Andy01DblCabTacoma: so I did what you suggested and can see where a lot of wires connect to black housing. I'm now trying to figure out how to physically accesse the area and pull out the unit to examine more. Thank you for your suggestion I feel like I'm getting somewhere.

 

I forgot to add the pictures I took

 

To gain access to those- remove the front seat (four bolts, and one wire connection for the seat belt indicator), remove the kick panel (they just pull straight back), and peel the carpet up.

That being said, the wires coming in from what you're calling the trailer harness, look factory to me. They are fuel pump, abs, locker (if equipped) and rear light related. Someone has obvious been in there though- I assume the blue wire is power to that under seat sub you had?

 

Thank you to all who have helped me. I'm embarrassed to say that I was wrong about trailer harness wire placement. I removed all the tape and zip ties encasing a slew of wires all bundled together. Then, I was able to accurately trace the wires to the rear lights. Also, this system was not factory installed. When purchasing my Tacoma, I was under the impression the wiring was factory installed. However, it was the Hopkins brand harness. Arghh. Now, I'll put the carpet back under front seat and install the Hopkins product.
My apologies to Blink1 for not following your suggestion. You were right.
Thanks again to all

 

sweet! glad to know you solved it