My Trailer Harness Is Bad

[wantahertzdonut]

Having just picked my truck up a short while ago, the first thing I did as soon as I had a hitch was check how my trailer hooked up. When I went to plug in the lights, I saw the expected corroded plug on the truck. And of course, no power to the trailer.

I cleaned the prongs as best I could, and still nothing, not so much as a flicker.

For the time being I have an add-on harness but I'm not a big fan of these, especially since there's a built in harness on the truck. But I have no idea where this harness leads to since it goes up into the body and disappears.

Is there a common failure point on these things or should I just chop the plug and put a new one on? Also, is there a separate fuse circuit? I'm still waiting on my repair manual to arrive so I'm trying to figure out where to start.

 

[Titanpat57]

So first things first...

Trailer worked fine with the other truck?

4 prong flat or 7 prong round?

Always, always, always start with the grounds....

Then chop the plug

Was previous truck different make than new truck??

Toyota (I believe) is wired differently than domestic trucks IIRC..

need more info, sorry for the barage of qustions..

 

[wantahertzdonut]

Trailer worked before and still does

4 prong flat

Where does the harness (I assume it's factory, correct me if I'm wrong but it looks like a factory install) ground out to usually?

The other "truck" is my IS300 with an aftermarket harness. So still a Toyota but not Toyota wiring

 

[stevec5000]

Probably just a blown fuse. Have you checked that?

 

[stevec5000]

Toyota (I believe) is wired differently than domestic trucks IIRC..

That's not true! How could it be wired differently, if it was nobody would be able to use it. My 2004 V6 has standard wiring, just connected the trailer cable and it all worked OK. It's easy to blow the fuse if you short one of the pins though.

 

[Titanpat57]

Trailer worked before and still does

4 prong flat

Where does the harness (I assume it's factory, correct me if I'm wrong but it looks like a factory install) ground out to usually?

The other "truck" is my IS300 with an aftermarket harness. So still a Toyota but not Toyota wiring

as crazy as grounding problems can be...remove all possibilitites and go right back to the battery, and add one to the frame as well..I always spray it with clear laquar after shining it all up.

I'd splice a new tail in..solder and heatshrink.

 

[TechWrench]

Having just picked my truck up a short while ago, the first thing I did as soon as I had a hitch was check how my trailer hooked up. When I went to plug in the lights, I saw the expected corroded plug on the truck. And of course, no power to the trailer.

I cleaned the prongs as best I could, and still nothing, not so much as a flicker.

For the time being I have an add-on harness but I'm not a big fan of these, especially since there's a built in harness on the truck. But I have no idea where this harness leads to since it goes up into the body and disappears.

Is there a common failure point on these things or should I just chop the plug and put a new one on? Also, is there a separate fuse circuit? I'm still waiting on my repair manual to arrive so I'm trying to figure out where to start.

You don't mention what year your vehicle is. But, I am pretty sure all 4th gen runners have a 7-pin round trailer wiring outlet, if the towing package was installed. If you have a 4-pin straight connector on the vehicle, then it is either an adapter from the 7-pin connector, or someone re-wired it.

 

[Pikeman]

The harness usually goes up through a notch in the bottom of the cargo floor and then into one of the sides behind the plastic trim panel. There is a converter box that plugs into the tail lights and then goes down to the plug. The Toyota's are wired different than other trucks in the fact that it is 5 wires coming from the tail lights into the magic converter box that turns it into a 4 prong. I believe these are in the 4th gens with out tow package and positive they are in the 3rd gens. My magic converter box went out and was easily replaced by a Hopkins part. If you read an older thread in this section started by member Kung it talks about this procedure. Hope this helps you in your quest for solutions.

http://www.toyota-4runner.org/towing/104319-hopkins-vehicle-wiring-kit.html