01 Access Cab Trailer lights wiring?

I have an 01 Tundra SR5/AC, came to me with one of those after-market, plug and play trailer wiring harnesses, but it wasn't working.. It was older so I assumed the converter box was blown... so I bought a new one (Specifically the

$51 CURT 55378 Vehicle-Side Custom 4-Pin Trailer Wiring Harness, Fits Select Toyota Tundra , Black

CURT 55378 Vehicle-Side Custom 4-Pin Trailer Wiring Harness), plugged everything in (including the connection to the battery)... but still nothing. I've checked every fuse in the truck, all of the truck's brake and signal lights work normally, confirmed 12v where it connects the battery to the truck's harness in the engine compartment, but I don't seem to be getting any power to the trucks harness where the curt converter box plugs in under the bed (back drivers side)? What am I missing... Truck is rust free (no indication of any bad grounds), no signs of any wiring issues or previous hack jobs, no sign of any rodents chewing any wires or anything?

 

Have you checked out your trailer converter box behind driver side rear combination light(backup, turn signal, tail light) if you have one or checked the 11 pin T 9 connector under the bed in that same location.

 

Uh... I don't seem to have one of those... ?

 

Early models did not come standard with any kind of trailer harness setup. Adding a converter was required. Even my 2000 Limited with all the options (laughable) did not come with a hitch or harness. I added both, used the Curt box similar to yours but circa 2006. There’s a series of connectors under the bed back there that send the signals out to the tail lamps. Run those wires and make sure there’s nothing unhooked or corroded or broken

 

My apologies in advance for any dumb questions... I hate messing with vehicle wiring, I normally don't normally mess with wiring beyond replacing the stereo head unit...
but I thought the curt thing I bought was the converter?

 

Same for my 2000 as well. I had to buy a bunch of stuff from Etrailer to make it plug n play…well most everything was plug n play. I did have to route and crimp my own 2 conductor wire for the trailer brakes.

 

It should be what you need

 

Any details or part numbers you needed? I don't need any trailer brakes, just trying to get the lights working

 

Have you tested the output of the new harness once installed?

 

OK I think I found at least some more info... the folks at etrailer say that this center connection/black wire on the truck's connection should be 12v constant, but I'm getting nothing. Anyone have a wiring diagram that shows where that wire is coming from?

 

That is the T 9 Trailer Converter connector. The black wire should indeed have 12vdc. That black wire goes up to the engine bay to a 1 pin Option Connector O 3 which is beside the battery. The Curt harness has a inline fuse that was tied to positive of battery. That conductor plugs into the O 3 Option Connector. Check that fuse and/or O 3 connector.

If that fuse is good, connection to batt is tight and Curt connector plugged into O 3 good, the next place it could be missing is the I 4 connector at the drivers kick panel. Panel by parking brake.

 

I checked fuse that came with the Curt, and confirmed 12v where that plugs into the truck's harness in the engine compartment... Do you have any more info on that I4 connector is that a fuse or what should that look like?

 

I meant to type IA4 and it is a 26 pin white connector behind drivers kick panel, big and kind of hard to miss. The 12vdc from O 3 connector goes to the IA4 connector pin 21 and is a black conductor also.

The below is my 04 DC LTD kick panel area and simply showing you for reference about where your IA4 is, which is where my IA6 is.

If it's leaving IA4 pin 21 with 12vdc, the next stop before it heads to the back is a 12 pin connector BB1 that's under the drivers seat. Pin 1 of that connector is where the O3 12vdc should be.

 

Awesome thanks...will check those this afternoon

 

I'm having this exact same problem. I'm trying to wire in my 3rd brake light and some LED lights in my camper with using the tow package wiring along with the curt harness. My 12v/hot black wire on the tow package harness that you have pictured isn't getting a reading from the back either. With BubbaW suggestions on this thread as well as yours here, I narrowed down my potential failure point it. However, I don't see the converter box when pulling my taillight out, were you able to find yours? I'll try to look around more, but it was not there nor was it under/behind the bumper the license plate.

 

No, but I didn't look around more, my understanding was that the Curt converter box does what that Toyota converter normally does (when installed)...

"I narrowed down my potential failure point" What is your failure point? I got super busy and haven't been able to do much work on it yet.. I did verify 12 volts at my IA4 connection under the dash but you have to pull the driver seat out to get to the BB1 connection which I haven't been able to do yet... (it's under the carpet under the seat...) If I don't find an issue there I'm going to assume it's in the final connection point and just jump it, running a wire from a confirmed 12v source to the curt converter.

 

Ah yea--I do see knabores response saying that our earlier year models didn't include those boxes. And I did the same thing you're talking about so far. I got readings in the cab under the dash as well as under the seat. That should narrow it down for me being somewhere after the grommet under the driver's seat running through the framerail to the back connection at the taillight. Some of the wire looms are just shoved up in there and on some points where there's a turn in/out of the framerail, it looks like its just tapped up real tight rather than in the wire loom. I was planning on checking points there under the frame for where it gets a reading, and where it doesn't--then just tap into the wire at the point that has the 12v reading and run it from that point down to the harness in the back.

 

I looked at (didn't test with multimeter) the wiring on the frame rail, mine is hard to see inless I pull the bed (which I'm not planning to do, it's mounted on top of the frame... my plan if the driver seat tests good with 12v, is to cut the black wire before it goes into the Toyota harness, and if it's good there just jump it... I'm also installing a backup camera so trying to do all this at once and hide the backup camera wires while I've got everything apart.

 

Yeah I can only see some of mine, but there are some spots I'd be able to get to/test--it doesn't help having my whole frame covered in wool wax either. Smart choice to do that all at once, I want to do that as well--but still need to eventually get one along with a new stereo (still OEM). You just gave me the idea to make sure I pull back the black wire right before the harness to see if it reads anything at that point--could save all the trouble going under the frame, and if it does read something, then we'll know it's that 11 point harness that's bad.

 

I finally completed my install today. I ended up finding an easily accessible point in the line right above the rear driver's side wheel. Pulled back the wire loom and found the black 12v hot and got a good reading. Ended up just tapping into and running a new wire from this point to the rear harness