2000 LX470 Trailer Harness Replacement

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gholsie

gholsie

10 Year 15 Year
Joined
Oct 1, 2009
Threads
11
Messages
54
Hey all, just wanted to share some experience I had today with a faulty wiring harness on my stock 2000 LX470. I first discovered the stock 3-wire converter was faulty when I tried to rent a trailer from U-Haul. At the time I tried to rent the trailer, the left turn signal was so weak, the trailer lights couldn't draw enough current. As a result, the trailer left turn signal wouldn't turn on and they refused to rent to me. After this wonderful incident, I decided to do some reverse engineering to find the problem. Looking at the forums, I noticed the stock converter module was typically bad and decided to replace it. Here's what I did.

First of all, I had to locate the faulty converter. On my rig, it was located behind the left drivers taillight. It was stuck up inside the rear quarter panel near the back window. I was able to reach up inside and pop out the old converter with a little force. The unit was double-sticky-taped in position. Anyway, the converter came apart easily by disconnecting the two connectors with a fingernail.

I then took the stock converter down to a local truck mod store and found an aftermarket converter module. The module was from Trailer Mate with a part number of 75375. Here's a link to the unit I found online: http://trailerpartstogo.com/75375taillightconvertersurfacemountdesignsmd.aspx

The unit reads:

Trailer Mate
SMD
Surface Mount Device
Circuit Protected
Taillight Converter
4.5 amps stop/turn
per side
7 amps taillights

I liked this module because it didn't require a special wire from the battery and would splice directly in-line using the existing harness connectors. It was also circuit protected in the case I managed to connect a trailer with a short.

Although I don't have a kit or tool to crimp new ends, I decided to cut & solder the existing wires. By doing this, I still have the ability to remove the module and replace again (if I ever need to). It also enabled me to solder on my workbench instead of trying to solder right next to the truck. To protect the solder joints, I used marine-grade shrink tubing. The marine-grade stuff has a glue that melts and seals the joint.

Here's the wiring pattern that I used:

Truck Side -> Module
Green -> Brown = Running Lights
Green/yellow -> Green = R/Turn
Green/white -> Red = Stop
Green/black -> Yellow = L/Turn
White -> White = Ground

Module -> Trailer Side
Green -> Green = R/T&stop
Brown -> Brown = Stop
Yellow -> Yellow = L/T&stop
White -> White/White = Ground

Anyway, this whole project cost me $25 and about 2 hours of work, not including my trip to Harbor Freight to buy the shrink tubing and a small LED connector I used to test the trailer end. :steer:

Hope some of you can benefit from the write-up. I know how this forum has helped me tremendously in the past.

Mike

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Good to know, thanks for sharing. I had to swap out the 7 round on my camper to a 4 way flat work with my LX (camper had trailer brakes, but not anymore). I've never tried the plug in on my LX, so we'll see if its operational today.
 
Thanks for the write up gholsie.

I had trouble with mine this fall for the first time and had to get mine jerry rigged to work.

So now I've got a temp solution in there for now and want to go ahead and move to an adapter that works with multiple plugs/pins.

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I also redid my trailer wiring this spring, except I made my own isolated system. I got a bunch of small relays meant for DIN rail mounting like these and shoved them back in there. Got a fuse holder and tapped into the 12V aux in the back corner. Works great, kind of funny hearing the relays click on and off when I brake.

I did screw it up a little so when you brake and have the turn signal on only the brake shows, will have to fix that in the spring.
 
SmoothLC said:
Thanks for the write up gholsie.

I had trouble with mine this fall for the first time and had to get mine jerry rigged to work.

So now I've got a temp solution in there for now and want to go ahead and move to an adapter that works with multiple plugs/pins.

47575.jpg
Click to expand...

My other truck has a 4-flat and a 7-round with brake brake controller. Nice to have both. If the trailer brakes were working on my pop up when I bought it, I might have added this to my LX.
 
Has anyone experienced a partially functioning trailer harness on their 100? I put a 4-way flat plug on my trailer, the trailer lights work prefect with my F-150. When I plugged the trailer to my LX, blinkers and brakes worked, but no running lights.

I'm going to plug the trailer to a third vehicle and see how it works. And then test the LX plug if the trailer works fine with a third vehicle. Wish I had one of these handy http://www.etrailer.com/p-i26.html

Update: I was able to plug my trailer into another vehicle, the trailer lights are working fine. I guess I'll diagnose the LX to figure out why it's not working right.

Seems to be a common issue:
https://forum.ih8mud.com/100-series-cruisers/29687-towing-wire-harness-recall-98-99-a.html
 
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TXLX100 said:
Has anyone experienced a partially functioning trailer harness on their 100? I put a 4-way flat plug on my trailer, the trailer lights work prefect with my F-150. When I plugged the trailer to my LX, blinkers and brakes worked, but no running lights.
Click to expand...

You probably have a bad unit like I did. Needs to be replaced.
 
I finally got around to fixing my tail light converter. I purchased a $12 unit from Northern Tool, it has blank ends on the wires. I was in a hurry earlier and just made it up with wire nuts to test if the tail light converter is the faulty component. It definitely is the problem.

One thing I noticed that wasn't mentioned, the aftermarket units include a white ground wire on the truck side and the OEM setup has 2 ground wires... One that bypasses the OEM converter. I just made it up like the picture shows and it works great.

I couldn't find my soldering iron today, so I picked up a $4 unit from Harbor Freight and a $4 4-way tester. I'll probably return the tester and I need the soldering iron anyway, I had shrink wrap, zip ties, and soldering metal.... I'm going to call this a $12 job and will take 1.5 hours if you have all the supplies ready. Thanks to Gholsie for the write up.
 
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TXLX100 said:
I finally got around to fixing my tail light converter. I purchased a $12 unit from Northern Tool, it has blank ends on the wires. I was in a hurry earlier and just made it up with wire nuts to test if the tail light converter is the faulty component. It definitely is the problem.

One thing I noticed that wasn't mentioned, the aftermarket units include a white ground wire on the truck side and the OEM setup has 2 ground wires... One that bypasses the OEM converter. I just made it up like the picture shows and it works great.

I couldn't find my soldering iron today, so I picked up a $4 unit from Harbor Freight and a $4 4-way tester. I'll probably return the tester and I need the soldering iron anyway, I had shrink wrap, zip ties, and soldering metal.... I'm going to call this a $12 job and will take 1.5 hours if you have all the supplies ready. Thanks to Gholsie for the write up.
Click to expand...

Hey TXLX-- Is this similar to the unit you used? http://www.northerntool.com/shop/tools/product_200625008_200625008
Price has gone up a little. I'm also considering the etrailer version that you originally were looking at: http://www.etrailer.com/t1-1999_Toyota_Land+Cruiser.htm
 
Dallas99 said:
Hey TXLX-- Is this similar to the unit you used? http://www.northerntool.com/shop/tools/product_200625008_200625008
Price has gone up a little. I'm also considering the etrailer version that you originally were looking at: http://www.etrailer.com/t1-1999_Toyota_Land Cruiser.htm
Click to expand...

No, I don't believe that's the one I purchased. NT has a pretty good selection of trailer wiring and such in the store. You really don't need the ends, just the controller part since you'll be splicing it into the existing harnesses. You could always buy a new unit from Toyota but I think it's like $80.

Amazon has a piece that might work - http://www.amazon.com/dp/B0002RNSPK/?tag=ihco-20
 
TXLX100 said:
No, I don't believe that's the one I purchased. NT has a pretty good selection of trailer wiring and such in the store. You really don't need the ends, just the controller part since you'll be splicing it into the existing harnesses. You could always buy a new unit from Toyota but I think it's like $80.

Amazon has a piece that might work - http://www.amazon.com/dp/B0002RNSPK/?tag=ihco-20
Click to expand...

OK-- I wasn't thinking about splicing into the existing wiring, which obviously makes the most sense. Ended up ordering this unit from Amazon, cost a little more, but still have option to splice. Appreciate the help!
 
Thanks for a great write up Mike. You saved me some time and money. I was troubleshooting weak turn signals and stop lamps on my trailer hookup. The trailer was fine so it had to be the LC. I replaced the POS Toyota part by splicing in the controller that you used (eBay for $27) and I'm back in business. Thanks to your write up, I didn't have to figure out which wire in the harness controlled what on the new harness. Entire process took about an hour. That would have been at least a $200 repair elsewhere. Thanks again for taking the time to detail the fix.

As a side note, I see Toyota had a recall on the controller for 1998 and 1999 model years because it was mounted under the vehicle near the spare tire. They assumed the exposure down there was causing the controller to fail. The recall relocated the controller to the cavity behind the left rear tail lamp assembly. I'm guessing it wasn't the location but a poorly designed Toyota controller that was the source of the failures. Mine was not covered by the recall as it was the first year that Toyota relocated the controller.


Moose
2000 LC
 
I had mine replaced twice by the dealer and still ended up at a uhaul with the desk guy helping me splice taillight wiring so I could rent their trailer. I eventually got the etrailer 118365 that TXLX mentions above. It's entirely plug'n'play and has worked great for 3 years now.

Dean

TXLX100 said:
That's what I figure as well. My LX never towed anything before now, so it's probably been broken for a while. I saw some threads about a possible recall for this, but I think it's just a TSB. Going to try this out as a replacement: 1998 Lexus LX 470 Custom Fit Vehicle Wiring - Tow Ready
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gholsie said:
Truck Side -> Module
Green -> Brown = Running Lights
Green/yellow -> Green = R/Turn
Green/white -> Red = Stop
Green/black -> Yellow = L/Turn
White -> White = Ground

Module -> Trailer Side
Green -> Green = R/T&stop
Brown -> Brown = Stop
Yellow -> Yellow = L/T&stop
White -> White/White = Ground
Click to expand...

Finally got around to replacing the wiring harness. @gholsie - your diagram and photos were a life saver! I cut out the original Toyota "15 amp Taillight Converter" and spliced in a Tekonsha 118365 T-One Connector Assembly purchased from Amazon. As gholsie pointed out, the converter is tucked up above the driver side brake light. Removing the light is the easiest method to get to the harness.

Slightly confusing is the number of wires and colors coming from the original converter compared to the replacement- note that one ground (white) wire is jumped from one connector directly to the other (pics attached), bypassing the converter altogether. Also, you'll have one extra ground coming from the new converter box that does not splice into the existing harness. I used water tight heat shrink butt connectors. Crimped on and heated, they create a great connection.

Hope this helps clarify a few details if anyone tackles this.

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No controller behind my drivers side rear light. I do have the connector under the passenger side. I bought the etrailer harness hoping for plug and play but lights aren't working correctly.

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