Trailer light wiring harness

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Ronel2020

Ronel2020

Joined
Aug 14, 2011
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I have been trying to fix a blinker on a boat trailer that was not working. I have rewired the trailer an replaced the liights but I still have the same problem. I also changed the harness at the bumper and I still have the same problem. What else should I look for in the LC? Seems like the problem has to be there. Thanks.
 
How deep into the wiring did you go when you replaced it? The problem usually lies in the trailer controller which is notorious for shorting out. If you haven't replaced it, that is probably your culprit.
 
Where is the trailer controller located?
 
Sorry. Normally I search before posting, but was getting frustrated while working on the lights today. I appreciate all of your help.
 
Have you made 100% sure it works at the trailer connector? Like, have you tested it at the plug with a 12 V power supply and gotten the correct lights to light up? A cheap multimeter will also tell you if you are getting the proper voltage on the truck side of things. Grounds can go bad real easy.
 
Yes. I checked the lights. I assumed it was the trailer because boat trailer lights burn out all the time (I live near saltwater). I changed them out and have the same problem. I then checked various wires on the trailer and even hooked some lights directly to the wiring harness and ha the same problem.
 
petrotk40 said:
How deep into the wiring did you go when you replaced it? The problem usually lies in the trailer controller which is notorious for shorting out. If you haven't replaced it, that is probably your culprit.
Click to expand...

petrotk40 said:
usually it's hiding in the jack cubby. little black plastic box. there are a number of threads on the subject if you do a quick search

I had the same issues https://forum.ih8mud.com/100-series-cruisers/530821-urgent-rth-trailer-wiring.html
Click to expand...

Does anyone know where this is in a 2000 LX? I looked in the jack cubby and didnt find it. Also does anyone have a picture of one?
 
Im confused, cause the truck with a factory hitch and 4 pin wiring. The 4 pin harness goes a plug just above the resonator on the passenger side of the truck. But all these threads say that the OEM converter is on the driver side.

Did Toyota just want to waste a bunch of wire?
 
I'm right there with you. I have no idea where all the wires go. I had an rv shop fix me up and have no idea what they did but my trailer lights work now.
 
The plug near the resonator is wired to the factory tail lamps. The factory converter plugs in there and the wiring harness runs up in to the body and resides near the DS tail lamp. This location is simply for protection against the elements. An aftermarket converter might just be mounted near the resonator.

One, theoretically, could wire directly to the plug near the resonator without a converter but this is not standard practice. The converter not only converts the signal when needed but it also keeps the trailer wiring separate from the vehicle. The better converters supply it's own power; the input wires are just used as triggers.
 
Last edited:
Tap the wires near the resonator for the appropriate power signals and send that to an aftermarket converter with isolated power from the battery. I mounted that converter right behind the DS tail light. Pretty tough to access or see from the jack cubby.

That plug near the resonator has the non-converted wires (right turn, left turn, running lights).
 
hoser said:
The plug near the resonator is wired to the factory tail lamps. The factory converter plugs in there and the wiring harness runs up in to the body and resides near the DS tail lamp. This location is simply for protection against the elements. An aftermarket converter might just be mounted near the resonator.
Click to expand...

So, the factory converter sits behind the DS tail light, and has a harness that runs inside the body to the PS and comes out of the body over the resonator. From the there the OEM 4 pin trailer harness connects to it?

This^^ is how I "think" it is setup.....granted i still havent found the OEM "converter box"

The plug that comes out over the resonator on my LX is converted, which is the opposite of what Eds Cruisin said.....

I just want to make sure I have this figured out before I start taking things apart.
 
pman said:
So, the factory converter sits behind the DS tail light, and has a harness that runs inside the body to the PS and comes out of the body over the resonator. From the there the OEM 4 pin trailer harness connects to it?

This^^ is how I "think" it is setup.....granted i still havent found the OEM "converter box"

The plug that comes out over the resonator on my LX is converted, which is the opposite of what Eds Cruisin said.....

I just want to make sure I have this figured out before I start taking things apart.
Click to expand...

Are you sure it's converted? Test each wire.
Unconverted they should test independently for each light. That means brake lights are separate from turn signals.
I did not have the tow package or any converter on my truck, and I used that plug near the resonator for a source to my converter.
 
I wouldn't be surprised if there were different OE wiring set-ups. I believe mine to be the revised version since I purchased it from Toyota in 2005 or so. My 100 had no tow hitch and the connector near the resonator was dangling... might've just had some tape over the connector... maybe a cap, I'm not sure.

Follow your 4-pin and snap a picture of the next connector to which it leads. Perhaps there is no box. This is petrotk40's pic. Is this the connector where your 4-pin is directly attached?

bc7e855e.jpg
 
Yes, my 4 pin is attached to that plug. Im assuming (hoping) that plug goes to the oem converter box that is supposedly behind the DS taillight.
 
hoser said:
I wouldn't be surprised if there were different OE wiring set-ups. I believe mine to be the revised version since I purchased it from Toyota in 2005 or so. My 100 had no tow hitch and the connector near the resonator was dangling... might've just had some tape over the connector... maybe a cap, I'm not sure.

Follow your 4-pin and snap a picture of the next connector to which it leads. Perhaps there is no box. This is petrotk40's pic. Is this the connector where your 4-pin is directly attached?

bc7e855e.jpg
Click to expand...

My truck harness is out. I cannot use just any harness from places you see off internet. Using this will cause a feedback in the dash. So this morning, I've ordered Hopkins "Short Proof Power Converter" this morning. I plan to tie that into the light signal wiring behind the jack. But seeing the picture, I am now wondering if I could tie to this instead? Take out harness and use the converter instead?

What say you?
 
Yes, I'd take the signal from the connector back there. Of course, you are going to double check if this is the correct plug. You can probably even buy the OEM connector, if you don't already have one plugged into it. Let us know how it goes, I might just go the same route as my trailer turn signals seem to be intermittent, using the OE converter box.
 
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