Mornin' my fellow Yota folks!

I have an '02 T4R SR5 4WD which has the OEM 4 Pin Flat trailer connection. I need to convert it to a 7 Pin Blade connector.

My girl bought me a boat! The trailer has the 7 Pin Blade setup but there are no plug-n-play adapters available on the market to make the connection so I purchased a Reese Towpower 85343 adapter I need to do some wiring with. The package is due to arrive today. The technical support guy at Reese said I'd just need to:

> ground the ground wire
> splice a wire into the backup light circuit

So my question is... Which wire color(s) should I be looking for when I splice into the backup light circuit? I know I'll be tapping into the driver's side taillight wiring but that's about it. I'm very confident when it comes to mechanical stuff but I'm somewhat not confident when it comes to wiring, LOL. If anyone has done this upgrade PLEASE advise. Much appreciated & thanks in advance!

NOTE: BTW, the trailer has hydraulic surge brakes but last night I completed the front & rear '02 Tundra brake conversion for added braking capabilities and I also ordered a transmission cooler which I'll be installing when I get that package.

 

You will have to pop a tail light, look for the reverse light bulb and id the wire colour, then find it in the bundle inside the left panel in the trunk, the 6 wire to 4 wire trailer light converter should be there aswell, you will want to splice at this location to avoid corrosion. I'm surprised the trailer has reverse lights, we usually unplug the trailer lights when launching a boat to avoid burning up bulbs, must be a fancy led setup with waterproof trailer lights and reverse, interesting, I'd probably skip the reverse lights myself.

 

Isn't there a thread somewhere about a 7 pin conversion but it was mounted under dash & wiring out back towards trailer? Mebbe electric brake(s) set-up?

 

^ Yes that is for the electric brake setup, he has a surge brakes that sense pressure on the hitch assembly and applies trailer brakes accordingly.

 

Thanks for your reply, Malcom99. I don't think the trailer itself has reverse/back-up lights. I do know the trailer has all LED lights. The reverse/back-up light connection* is explained below...

I just got off of the phone with Reese Towpower's Tech Support (1.800.632.3290). This is what he said for my application...

> The BLUE wire DOES NOT need to be connected because I have hydraulic surge disc brakes. This wire is for trailers requiring an electronic brake controller.

> * The YELLOW wire DOES NEED to be connected to my reverse/back-up light wiring. When I select reverse on my shifter the electrical signal that powers on the white colored reverse light bulb will also send a signal to the hydraulic surge disc brakes' circuit to NOT actuate the hydraulic disc brakes because I'm backing up the trailer. Because when I back-up, the hydraulic surge system will compress/actuate and this obviously wouldn't be ideal because I don't want the brakes applied when I'm trying to launch/trailer our boat.

> The BLACK wire DOES NOT need to be connected because I'm not running a charger on my boat trailer. This is applicable for folks towing a travel trailer.

> The WHITE wire DOES NEED to be connected because I will need to ground this adapter.

But I still need to figure out which wire I need to splice the YELLOW wire into on my reverse/back-up light wiring. I'm assuming there are only 2 wires I need to test. I'll find out shortly. I was just hoping someone already performed this project and knew the wire color I needed to tap.

Other than that I'll also need to drill and tap a hole(s) on the bottom of my tow hitch to accommodate the larger connecter/adapter bracket.

 

Unfortunately, that was for a setup using an electronic brake controller. My trailer utilizes a hydraulic surge disc brake system. Thanks for your reply though.

 

Of course you would need to connect the reverse wiring for surge brakes, never thought about that my bad. It should be the red wire, forget if it has stripes, but some different years have different wire colours, as I mentioned before you are best to pull the tail light driver side ID the + reverse wire and chase it to the trunk and splice there with solder, do not use vampire clips to make this splice. open the tailgate remove the 2 bolts from the driver side tail light and push to the driver side to release tail light from rubber mounts, probably easier to do this than type out inquiries as to which wire it is, I added LED backups a year ago but don't remember the wire colours. CAD spelling

 

So this is how I ended up doing the installation...

Spoiler alert, Malcolm99. I had to use one vampire clip, LOL!


Here's the OEM 4 Pin flat connector I needed to upgrade to a 7 Pin blade connector.


This is where the 4 Pin flat connector harness plugs into my main wiring harness. There were 4 zip ties securing the 4 Pin flat harness.


I removed this rear floormat support plate.

Next I removed the driver's side tonneau cover holder.

Then I dismounted the rear portion of the driver's side deck trim cover so I could access the driver's side rear combination lamp assembly wiring harness.

 

I then removed the driver's side rear combination lamp assembly so I could see what color wire I needed to splice into at the connector. The reverse light is located at the very top of the lamp assembly.

The reverse light wire I needed to tap into is the RED one w/a BLUE stripe.



After I made the connection I began routing the wire...

I punched a hole in this plastic cover located on the floor between the edge of the carpet and the hatch weather stripping (the smaller of the 2 plastic covers in that corner).

I crawled underneath and found this existing hole. I illuminated the hole with a flashlight and looked from above to confirm where I needed to feed the wire through.

You can see the light shining through the hole. (I temporarily put the plastic cover back on in this photo)

I used gaffers tape to secure the wire.

 

After I fed the wire through I re-installed everything I removed and crawled back underneath to begin the rest of the work.


To help keep the wire from rubbing itself raw over time I slipped the wire through a piece of vacuum hose and secured the vacuum tubing in place with a zip tie to prevent it from sliding downwards.


I removed the 2 bolts that secured the 4 Pin flat connector mounting bracket on the tow hitch.

I also removed the 2 small screws on the bracket that held the 4 Pin flat connector within the bracket.

Amazingly, the 2 holes on the old bracket were identical to the 2 holes on the new bracket.
BUT!!! It was too good to be true. I had to drill a couple of new holes because the 7 Pin Blade harness was pressing against my spare tire so I needed to move the new bracket rearward a bit.

 

I also had to cut off the heat shrink tubing from the harness and replace it with electrical tape to get a bit more flex so the harness could clear the spare tire.


I cut off the harness' yellow butt connector from the yellow aux. backup wire and replaced it with a male connector I could unplug if I needed to do so for some reason. (Sorry, I forgot the name of that type of plug.) I crimped the female connector on the wire I fed through the body from the reverse light then I plugged them critters together. Oh, as you can see in the photo I also slipped on another piece of vacuum hose and secured it with zip ties to keep the yellow wire from rubbing itself raw on that black bracket.

I also cut off and replaced the harness' white ground wire ring terminal with a slightly larger one because it wouldn't fit over the ground location I chose. As you can see in the photo I used the bolt to ground the ring terminal.

I plugged in the male and female 4 Pin flat connectors then tested the 7 Pin connection for ground and tested it for the 12V signal when selecting the reverse gear. Thankfully it all worked out!


The harness is pretty close to the tire. I'll have to monitor it to see if I need to make a thingy to move it a bit further away. At least it's not crammed up against the tire like it was, wheew!


And there she is!

 

I'll update this post when I tow our boat for the first time.