Trailer Brake Controller Wiring without Factory Tow Package

I am in the process of gathering the parts needed to set up my Taco for towing a trailer with electric brakes. Sadly my truck does not have all the wire in place to support trailer brakes. I really want to follow as close to factory wiring as possible and was wondering if anybody has already done this and what terminals or "repair wires" were used? I was able to find the following documents to help and they seem to be the same as my 2008:

2006 Tacoma Manual EM01D0U
2007 Tacoma Manual EM03N0U
1991-2005 Toyota Wire Harness Repair Manual RM1022E

First I located the Towing Brake Controller connector T7 (EM03N0U page 247) which is a 5-pin Female terminal connector tucked behind the left kick panel in the cab. This connector can also be identified in EM01D0U page 308 as Toyota part number 90980–11603. Using the part number, this connector may also be located in RM1022E page 74. On my truck this connector was fully populated with wire so I need to first trace the trailer brake power (+B) T7 pin 2 (Black Wire) back to connector IA4 pin 1 which is also buried in the left kick panel. The engine compartment side of this connector pair is missing the black wire in IA4 pin 1 so I need to find a terminal to use so I can run a new wire.

Toyota makes 160mm long "Repair Wires with Terminal" for about $5 ea. which is a painful price but is cheaper than buying a special crimp tool! So for the missing IA4 connector pin 1, I looked in EM01D0U page 301 to see drawings of the connector bodies. Next I looked in RM1022E under "<FEMALE> 11P Non–waterproof Type" and found a matching connector drawing on page 88. Now near as I can tell, this is the connector that already has the black wire populated in pin 1 position so I need to find the mating connector which should be found under "<MALE> 11P Non–waterproof Type" on RM1022E page 214 but the pictures do not quite look right... I figured the connector part numbers would probably be similar for both mating connector bodies (Female 11539, 11712 probably mates with Male 11538, 11711). Looks like 11538 and 11711 both point to repair wire 12330. So I should be able to splice a new black wire and run it through the firewall and terminate in the engine compartment fuse box. Has anybody done this already and is repair wire 12330 the correct one for connector IA4 (engine compartment side)?

Looking at the fuse box end of trailer brake power, the 30A fuse normally labeled "30A TOWING BRK" is missing and no surprise only the battery side terminal is present and not the load side terminal. What terminal part number are we to use for the load side of the fuse? Seems this question has been asked before but I have not found a definitive answer yet... Using RM1022E and doing a word search for "Fuse" comes up with repair wire 82998-12810 for a mini fuse, 82998-12820 for a mini-fuse low-profile and 82998-12140 for a blade fuse repair wire. I'm guessing 82998-12140 might be the one, does anyone know for sure?

Now for the brake controller BRK signal output from T7 pin 1 (yellow) to connector ID2 pin 8 in the left kick panel. Well this wire is in place on my truck, however the female mating terminal and wire in ID2 pin 8 is missing and normally heads to the rear of the vehicle to the trailer plug interface connector BE1 and then to the 7-pin trailer connector T12. My truck has a 4-pin trailer plug so I need to add in this missing yellow wire from the cab to rear of the truck. To find a "repair wire" for the ID2 female connector body, I looked in EM01D0U on page 301 for the connector body drawings. Then look for the same connector in RM1022E and find it on page 91 and crosses to connectors 11531, 11693 and 12351. Using these numbers within RM1022E crosses to repair wire 12340. So theoretically using repair wire 82998-12340 spliced to a yellow wire run to the rear of the vehicle should allow the trailer brakes to operate. Can anyone confirm this is the correct repair wire to use?

After all of this, it still leaves two wires missing for the 7-pin trailer connector. The gray wire for trailer battery charging and the red/wht wire for the back up lights. These two circuits are not as critical but I will probably pull them in since I have to go to the trouble of pulling the yellow brake wire from the cab to the rear anyways.

-Bill

 

Hey Bill have you had any progress on this? I have a 06 with the dealer installed package, I was hoping to somehow utilize the factory plug but the more I look into this the tougher and more convoluted it appears to get.

 

Hi FilthyOx,
Nope, no progress yet as I was hoping that someone else had already gone down this path... It must be time to just order the repair wires and see if they fit! I really dislike in-line fuses so I'm hoping the repair wire for the main fuse box fits! I will post again with either good news or bad...

-Bill

 

Well I got back to the trailer wiring project this weekend. I decided to not use the repair wire approach since economical, low-use crimp tools are available for about $30 and crimp terminals are available for about $0.25 each.

Most of the missing wires and terminals for the brake controller use Sumitomo/Yazaki Type 2.3II (090II) style terminals available from places like:
http://www.bmotorsports.com/shop/index.php/cPath/109_110
https://www.theplugdealer.com

Crimp Tools for Weather Pack and Metri-Pack 150 & 280 appear to also work on the Sumitomo/Yazaki Type 2.3II
Performance Plus WHPT-11 (More terminal selections but not as good on weather pack seals)
Casper Electronics 103021 (Better for weather Pack)

The hardest terminal to track down is the one used inside the engine compartment fuse box. I believe it is typically repair wire 82998-12140 which appears to use Sumitomo fuse terminals. I found two sources for what I believe may be the correct terminals and placed an order with cycleterminal.com for both the 12-14 AWG and the 14-20 AWG size terminals. I also purchased an inexpensive crimp tool here as well but will probably order another one like those mentioned above as you can never have too many tools!
http://www.cycleterminal.com/atc-fuse-box.html
http://easternbeaver.com/Main/Elec__Products/Connectors/FuseboxTerms/fuseboxterms.html

-Bill

 

I received my GXL wire and terminals and set out to install the new 7-blade trailer plug and brake controller. I pulled the engine compartment fuse box to install the trailer brake #12 Black wire on the unpopulated 30A trailer brake fuse. Sad thing is the terminal I thought would work does not fit at all. So I took the opportunity to eject a terminal from the fuse box, measure and take its picture.

After taking pictures of the disassembled fuse box, I noticed "Delphi" embossed in the plastic so I'm betting the terminals are a Delphi Packard part. Anyone recognize this terminal?

The day was not a total bust, I was able to run trailer brake wiring and install the 7-blade trailer receptacle. I was going to use the factory controller wiring but saw that the factory used ~ 16AWG for the controller battery and brake output. This is a 30A rated circuit so I bypassed the factory wiring and installed #12GXL which is 125C rated wire and can handle the amperage. Well onward and upward, need to locate the correct terminals for the engine compartment fuse box...

-Bill

 

I found the engine compartment fuse box mini-fuse terminals. They are Korea Electric Terminal (KET) ST781034-3 (M 18-16 AWG) and ST781035-3 (L 14-12 AWG). Still have not found anyone that carries them in small quantities. Anybody know of a supply?

-Bill

 

Here is a picture of the Engine compartment fuse box relay terminal. This is the small one similar to a .187 spade terminal. The larger terminal looks the same and is similar to a .250 spade terminal. These are the ones that fit the light blue DENSO relays in the fuse box. I have not located a possible source for these as of yet.


-Bill

 

If you are interested in how to get into the engine compartment fuse box, this might help...

1) Disconnect the battery first thing.

2) Remove fuse box cover and release the engine harness end plate.

3) Disconnect primary cable and unplug the engine harness.

4) Release the clips holding the fuse assembly to the lower enclosure. This takes very light pressure with a small flat blade screwdriver. Gently pull up on fuse assembly as you release the clips.

5) Lift the fuse assembly out of the lower enclosure being careful not to stress any wires.

I tried to remove the lower enclosure from the fender well but they zip-tied an air-bag harness to the bottom of the enclosure so I just used an inspection mirror to work on the bottom side of the fuse assembly instead... Actually when inserting terminals, you can look through the terminal opening and guide the terminal into the housing position.

-Bill

 

All the wiring is now installed except inside the fuse box... I mounted the Tekonsha P3 controller in the little pocket to the right of the steering wheel. I angled it so that there was good access to the manual lever but it makes it not exactly parallel with the truck body. I'm hoping this will not cause a problem, any one else mount their P3 at a slight angle and have problems?


The drivers side license plate light gave way to the 7-blade RV trailer receptacle. Between the license plate and the receptacle is the Schrader valve for my rear air bags.


Almost ready to tow if I can just find a source for the KET fuse box terminals!
-Bill

 

My '13 DC 2.7L did not come with the factory tow package, but I installed most of it. This was 3 years ago, so I don't remember all of the details. I ordered the factory accessory harness that was a 4 pin connector. It was plug and play, but required a lot of time. When running the wiring I also included the 5th wire for the trailer brakes. While I did use a 7 pin connector, I did not run the 12V constant or the back-up wires. I have the same brake controller, but decided to hide it. I tow 0.01% of the time. I put it in the center console arm rest. Since I had most of the interior apart I also ran a constant 12V outlet in the back of the console, which has come in handy. The 12v outlet and brake controller were wired to the battery with some fuses (bolted to the engine compartment using existing holes). The install came out really clean. It looked factory enough that the service techs couldn't tell. I towed a 3500 lb trailer cross country with no issues.

 

Hi Bill,
where did you buy the terminal, which is in the photo on the left? And what is the code of the terminal? I am trying the terminal a long time to buy, but I can not find it anywhere.
Thank you for your response

 

Hi Lukas,

The terminal on the left I purchased from Cycle Terminal, the link is at the bottom of post 4. What is shown on their web page is the ATC size terminal, what is shown in my picture on the left is the ATM size terminal which I don't think is advertised on Cycle Terminal. Email Joe and ask him if he still has some of the ATM terminals, he was super helpful when I was looking.

Edit - I think the manufacture of the terminal is Sumitomo, sorry I don't know the part number...

-Bill

 

So if I understand correctly - it's not possible to just buy OEM wiring harnesses, plug them in and run them from underneath the dash all the way back is it? You have to find wire and terminals to match, and add them.

I'm in the process of buying a small travel trailer and I'll need electric brakes.

If you had to do it again, would you buy an aftermarket kit, or do it the way you did?

Thanks for your input!

 

If I may join this discussion...

I have just (mostly) installed a 7-pin trailer hookup on my 2000 Tacoma. The 2000's did not come pre-wired, so I've done it manually. I got an adapter just for the lights that plugs into the taillight/turn sockets. That was easy. For the trailer brakes, I got a Tekonsha Voyager with just an unterminated adapter.

The hard part (I do mean hard) was connecting the red wire on the controller harness to the cold side of the brake light switch. A couple of uncomfortable hours lying on my back in the from floor board finally accomplished that. I ended up soldering this 'cuz I could reach up in there with a soldering iron better than a crimp tool. It helped to remove the panel under the steering wheel.

For the rest, I ran the three wires through an existing grommet into the engine compartment. The ground went to a fender connector right next to the battery. The black power wire was ring connected to the + side of the battery with a 30A inline fuse. The blue wire to the trailer brake I ran down along the frame to the trailer connector.

OK, one thing not done, and a question - I want to hook up the trailer power line. Where can I hook that into a solid 12V that turns on atthe Accessory position? I thought there would be something near the back of the truck, but the more I look, I don't think so. Will I need to run another wire up to the front and find a line coming off the ignition switch? Should have done it all together shouldn't I?

Thanks,
RandyTac

 

Wouldn't you want that one powered all the time? (IE, trailer interior lights, etc) or is that what the aforementioned black power wire was for? Other than that, I'm no help, but I was curious about that.

 

Well, that's a good question. I was thinking I'd want it powered only when I want it powered. Otherwise, the RV battery will be draining the truck battery all the time it's plugged in. Does anyone know what the usual protocol is for the trailer power?

thanks,
RandyTac

 

both my 01 and my 07 Cummins had them wired constant power. Just fyi. I always had good batteries - but I never ran them dead when I had my camper on either. And I was never very stingy with my light use or heater use either. Could always just unplug the trailer overnight if you didn't want to worry about it.

 

There are wiring kits available but to my knowledge none of them connect into the factory fuses and relays used in the factory towing packages. I think one of them is Part Number:

$155 08921-04960 Towing Wire Harness

08921-04960. Why they removed the trailer wires from the engine compartment fuse box is beyond me, saves a few feet of wire but now they have to stock a different harness... I ended up splicing in to the factory wiring near the connectors with larger wire as the factory wire is smaller than the brake controller manufacturers recommend. For me, I would still do it the same way but I really wanted to use the factory fuse positions in the engine compartment. -Bill-

The factory trailer wiring (see pdf attachment in post #19) uses a relay to turn off the battery power to the 7-pin trailer plug when the ignition is turned off. This is to prevent your trailer from draining your truck start battery. This is typically referred to as a battery isolation relay or as Toyota calls it "BATT CHG Relay". I ran the wire for mine but did not hook it up on the battery end. I plan to use solar or shore power to charge the trailer battery. I am also using an AGM battery in the trailer and it does better when not charged above 14.2 V, something not guaranteed if connected to the truck alternator which uses a flooded lead acid battery. I suppose one could install a charge controller between the truck battery system and trailer battery to prevent over charging the trailer AGM battery. In any case, I would always have a means to separate the two battery systems outside of yanking the trailer plug. -Bill-

 

Since I could not locate a source of the KET fuse box terminals, the attached pdf shows how I ended up installing the 7-pin trailer connector on my truck which had the 4-pin connector already installed. If someone locates a source of repair wires or the KET ST781035-3 (L 14-12 AWG) terminals, chime in as I would like to use the 30A fuse in the engine compartment fuse box. I suppose a junk yard could yield a repair wire or two...