Bad Factory Towing Harness?

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

R

richg

Joined
Nov 16, 2005
Threads
14
Messages
213
My 98 LC did not come with a towing package. December of 05, I picked up a factory towing harness and installed it. It is a 4 pin flat harness. This worked fine for me with no issues up until a few months ago.

What is happening now is that the towing left brake light / blinker does NOT work. I can put a test light into the factory trailer harness pins and verify running lights and right blinker / brake but the left is non-functioning. All of the lights on the LC function perfectly without issue (with and without trailer hooked up).

I have verified continuity with grounds, ran a second ground all the way from the battery to the factory trailer harness ground location near the spare tire. Nothing seems to work.

Could the harness itself have gone bad? Something in the converter box? I'm at a loss here as to how a practically brand new harness could be bad? Does anyone have any insight or suggestions?

rich
 
If the signal is not at the towing harness, I would suspect the towing converter relay. I've never played with it, but mine is at the drivers side rear of vehicle. You can probably trace the harnes wires back to it.
 
I know exactly where the converter box is as I installed the harness :). Its located behind the drivers taillight. That is where I'm leaning towards as the failure, but its just frustrating that a practically brand new part as simple as this could be bad -- I bought the factory harness for the very reason I thought it would be the most reliable!

rich
 
It happened on my 4runner. Didn't work, they replaced it under warranty and I was on my way. I thought the exact same thing and wasted a lot of time troubleshooting the harness, grounds and such. It is electronic you know;)
 
Thanks for the info Doug, I appreciate it! I'll likely just order a new harness and stop pulling my hair out!
 
The converter box for my '98 harness set itself on fire under the car. We had it replaced and then Toyota sent us a recall notice. I'd give them a call and have them check the VIN to make sure yours is safe. If not they'll replace it at no charge.

Ben
 
You are better off bypassing the whole system with a new isolated relay box. It doesn't take long to run a new power wire to the back and put the box in the same location. At least then if the trailer shorts your relay, it will not affect the rest of your truck.
 
I wholeheartedly agree with EdsCrusin.
A new (powered) trailer converter will prevent damages in case you hook up a trailer with too high load (too many lights) or the occasional "dunking" and potential shorting of the trailer lights.

And a new converter does not cost much ($15-$35). You can even leave all the leads where they are and splice the new one in place behind the rear driver side light. If you remove the jack from its little cubby, you can even pull it out that way.

If you add a new powered converter, run a AWG #8 or #10 from a FUSED position on the battery. Where you attach the cable under the truck, ensure that you "double-up" on insulation so vibration and potentially shaved off insulation will not create a short. Needless to say, ensure you have a good ground point (maybe the most common problem with trailer lighting is lack of a good ground connection).
 
I had thought the factory converter did offer circuit protection -- part of the reason I went with a factory harness, but I guess I was wrong.

I did test the leads into the converter and all signals are present, but left brake / signal is dead right at the output leads of the converter. So something inside the converter did indeed go south.

Thanks for the replies

rich
 
No, the "only" thing the converter does is to allow us with separate turn and break signals (almost all non- U.S. cars) to join the leads and have combined brake/turn signals on the trailer.
No protection what-so-ever, apart from that.

You can buy "any" after market converter and splice in place. The existing leads are likely long enough to make it an easy mod. Splice, solder, and heat shrink. Protect it all with a sleeve to prevent any future shorts.
 
Hey guys!
We have this same problem with our 99 LX, What kind or after market converter should I buy? Where can I locate one (shop, store, online).... I tried bypassing the whole converter and consequently very little power/light was transmitted.... will an after market unit work just as well as the OEM...


oh yea and this is the 2nd time this problem has happened.
 
LexissLX470 said:
Hey guys!
We have this same problem with our 99 LX, What kind or after market converter should I buy? Where can I locate one (shop, store, online).... I tried bypassing the whole converter and consequently very little power/light was transmitted.... will an after market unit work just as well as the OEM...


oh yea and this is the 2nd time this problem has happened.
Click to expand...

I have found the best deals on E-trailer.com. They have everything you need to tow just about anything. They also have wiring diagrams and brake controllers.

The heavy duty isolated systems include their own power source (that you have to run from the battery), so power to the lights will not be a problem.
 
Wellcraft19 said:
It is not rocket science to fix, but here are a few on-line sources:

http://www.trailerpartsdepot.com/
http://www.etrailer.com/
http://www.hitchsource.com/
http://www.lowcosttrailersupplies.com/
http://www.marksrv.com/wiring.htm

Or, you can just go down to your local "Schucks/Kragen/Autozone and pick up a (non-powered) converter for some $15 and splice it in.
Click to expand...

Keep in mind that those non-powered units are not going to protect your wiring any better than the Toyota version. They are essentially the same.
 
There is a thread here somewhere about a silent recall on the tow harness. I know because when I had my 99 LC the dealer checked mine out and it was OK. If it wasn't they were going to fix it for free.
 
Just wanted to add a final follow up. I soldered in a new converter and all is well.

I also wanted to add a note about circuit protection though. The factory unit does indeed offer circuit protection -- it is stamped directly on the factory converter that it is a circuit protected unit. I ended up ordering this unit from e-trailer which also has circuit protection: http://www.etrailer.com/p-118175.htm .

I thought about picking up a powered converter as was suggested, but really wasn't in the mood to run more wires back from the battery after having done that when I installed my brake controller a few weeks prior.

rich
 
Here is the recall thread for the 98-99. My 2000 was re-wired and has both the 4and the 5 wire, shopping for a popup so I guess I will find out if they are bad on the 2000's as well.

https://forum.ih8mud.com/showthread.php?t=29687
 
My 98 had the recall work performed and still blew out the converter. I wouldn't waste time on the Toyota stuff. Just get an independently powered (isolated) "circuit protected" unit and run with that.

Good thread here for trailer wiring ...
https://forum.ih8mud.com/showthread.php?t=162182
 
Last edited:
Wellcraft19 said:
If you add a new powered converter, run a AWG #8 or #10 from a FUSED position on the battery. Where you attach the cable under the truck, ensure that you "double-up" on insulation so vibration and potentially shaved off insulation will not create a short. Needless to say, ensure you have a good ground point (maybe the most common problem with trailer lighting is lack of a good ground connection).
Click to expand...

I just did a powered converter switch. The hardest problem was finding a way to get the power wire into the rear of the truck. The damn things are airtight. The place where the factory brings its wiring into and out of the back was not usable... no room.

I worked it in from under the hatch and carpeting. Can't see it and I think it will not chafe.
 
You must log in or register to reply here.

Similar threads

L
Engine Wire Harness Clips
Replies
2
Views
586
loecruiser
L
lx470mg
Towing 7,840 lbs with 2004 Lx-470?!
2
Replies
25
Views
2K
cbbr
cbbr
smwmustang
Exhaust leak and bad catalytic convertor questions
Replies
0
Views
351
smwmustang
smwmustang
cbbr
Bad Alternator? Something else? High amp replacement?
Replies
4
Views
740
nissanh
nissanh

Users who are viewing this thread

Total: 1 (members: 0, guests: 1)

Share this page

Back
Top Bottom