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2012 f150 4pin to 7 pin no tow package, myths, truths, compendium of information

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Old 02-26-2013, 10:42 AM
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Join Date: Aug 2008
Vehicle: 2012 Ford F150
Posts: 9
Arrow 2012 f150 4 pin to 7 pin no tow package, myths, truth, compendium of information

Got this??
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And want this?

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…me too
I have a 2012 f150 XLT w/ 5.0 3.31 gears and no tow package. The truck was a rental for one year and has 27000 mi on it. I picked it up for a little less than 25000. It’s not loaded but has the necessary power options and the upgraded speakers, and cloth seats, aux input, but no sync. I love the 5.0, that thing runs like mad when you ask it to and gets 16 around town pretty reliably (when my foot is good), as calculated by hand and generally within 3 tenths on the computer. In any case it’s a nice truck and well priced but like many trucks on the road did not come wired for the tow package. This is the main myth I would seek to dispel is that not all trucks are created equal. I have seen it time and again on the forums where people say they are all wired the same, however I have proof otherwise. I wanted to do this write up to get as much of other peoples information in the same place and add my findings to what I feel is a most annoying issue. I WISH FORD WOULD WIRE ALL THE TRUCKS THE SAME…..PLEASE!!!!!! ……at least up to the 4/7 pin connection at the back of the truck...made for towing....i mean come on its down to 10 ft x 3 wires, and we just cant afford that???? Luckily the front of the truck does appear to be wired more universally.

Let’s start off by determining which truck you have….Follow the wiring harness back from the large plug under the hood on the driver’s side near the brake booster. The wire loom travels down over the wheel well and along the driver’s side frame rail, courses up over the rail to supply the fuel pump and fuel pump driver (located on a cross-member) then back along the inside of the rail to supply the taillights, and of course the trailer wiring.

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Click the image to open in full size.

The pictures below are of the frame side (toward the cab) of the trailer tow wiring. Notice the difference.
Left is a random truck on a ford lot and right is my truck. Notice that there are 7 wires total on left and 4 on the right (with the white ground just out of the pic.

The 4 pin on my truck (picture right below) comprised of:
white wire for ground just out of the picture
yellow and green for brake lights and turn signals
brown for running lights.

The left picture has:
white wire for ground attached to frame
yellow and green for brake lights and turn signals
brown for running lights.
*blue for brake controller function
*orange for trailer battery charge/trailer power, the line is only hot when the key is in the ON position.
*grey/brown wire for reverse lights
* indicates wires that are not accounted for and will need to be added in order to achieve full 7 pin functionality.

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If your truck has wiring that looks like the picture on the left you are in luck!!! You have the “plug and play” option in which case I strongly recommend that you ask ebay, taska, or your local ford dealership for part number 9L3Z15A416A, you will also need an aftermarket bracket, unless you pop for the ford hitch which has it welded on. There are several places to find the bracket. Here is a representation from etrailer.com.
Etrailer part number HM40978 .


sorry i know that pic isnt the best representation but it should get the point across if thats what you see in a dealer parts house

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Click the image to open in full size.

non factory option below

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So for the people finding themselves without the extra 3 wires you have a few options, most of which include some level of splicing. A fairly common option pictured above and found at most local parts stores, uhaul, and etrailer uses the factory 4 pin for the connections it has available then you wire in the rest. Etrailers part number is (C57674) from curt and is $28. I suppose one could still use the ford factory plug (part number 9L3-Z15-A41-6A) and splice into the wires of the plug. In that way you get the ford “look” of the factory option and get your splices up high which might save you some road grime, but let’s face it gets everywhere. The ford 7 pin plug should run you about 75 depending on shipping online or dealer price.
Now finding the wires to splice was a bit trickier, at least until I noticed the wires into and out of the plug in the engine bay. Notice in the top picture there are far more wires in than there are out to the rear of the truck. Immediately I recognized the large orange wire for the trailer charge, and the large blue brake controller wire. I highlighted the orange wire below, and blue is easy to find in that bunch as well. The reverse light signal wire is found in the small plug just next to the large harness in the direction toward the engine. That bunch of wires also contains:
-green turn
-yellow turn
-brown running light
-grey/brown reverse light signal is still confusing because it is wired with the same color wire as the left truck brake signal. The two wires are next to each other and the one that lit up for my trucks reverse signal was the outermost wire, so this is what I will be tapping into for reverse power. I highlighted it below to illustrate better.
-Blue/white is the truck reverse lights, I would not use this as a signal wire without a relay as this wire is a small guage
-Purple/orange is the right truck brake signal
-Gray/purple (hard to see color in pic below but its in the same row as green at the opposite end…looks just grey) I was unable to get to light up, and may be for something like reverse proximity sensors or camera on equipped trucks, maybe someone could put a test light on it and tell us what activates it.

In any case I tested the orange wire in the large bundle and there is continuity between there and the #9 spot on the fuse panel which houses the trailer tow relay! I haven’t found a way to test the brake wire but I assume this being the origin of all the rear electrical it should carry the correct voltage as long as you make nice connections. I felt this was the ideal place to splice the wires in because again it’s high away from water, easily visible, and gives a nice bundle of wires to follow for a safe course back.

Click the image to open in full size.

Seeing the entire trailer wiring harness end at this point made me think that you could just swap out the rear harness with a junk yard truck, or rear harness kit…….. and sure enough Tasca does have a rear wire harness for sale part number (BL3Z-14405-DGA) which may offer a non splice solution, but you should check that out with them to be sure it has the wires mentioned above before handing over your visa. Of course keep in mind that you would need to drop the fuel tank to reach some of those connections, but if you have the help could be a nice solution priced around $170.

Click the image to open in full size.

The fuses we need to add in order to power the system are largely in place, but there are some we need to add. Trailer charge power is routed through the #21 fuse spot (right of the blue one under the relays) and should be a 30 amp. Spot #9 should have a relay to complete the circuit. My truck does not have rear defrost so I cannabilised the #4 relay for that purpose… when you purchase the brake controller kit from ford it will include the relay. The manual highlights several other fuses and relays for trailer tow power, and just for completeness ill run through them;
#6 TT Park lamp relay
#9 TT Battery charge relay
#17 TT Trailer brake 30A
#21 TT Battery charge 30A
#37 TT Lt stop/turn relay
#38 TT Rt stop/turn relay
#39 TT Reverse lamp relay
#43 TT reverse lamp 15A
#67 Park lamp relay
#73 TT turn/stop power 40A

And finally the brake controller

[url=http://www.f150online.com] Click the image to open in full size.

Brake controller part numbers I found: BL3Z2C006BA, BL3Z2C006BB, and BL3Z2C006AA. I am pretty sure they are all the same in function but were dedicated to different trucks based on package. The brake controller wiring is found in either one of two places. Plugged in behind the driver’s side coin box, or taped up next to the OBD test port connection under the steering column. I read somewhere that in all the later trucks they put it by the OBD port to make it easier to access. The wires here can be used for connecting up an aftermarket controller, some of which I believe even come with a plug to fit the stock plug which is nice. The trailer brake controller can be installed into the existing coin tray slot in the instrument panel and plugged in for vehicles factory equipped with trailer towing package. Your truck will then need to be reflashed at a Ford dealership for the instrument cluster to function properly with the new brake controller. Below are the etrailer options.


Here is a youtube demonstration of a controller install by midevilone on youtube.

Personally I like the stock controller because once you get it integrated it delivers simultaneous progressive braking as you increase your braking force, plus you get the nice clean stock look.
Comments, suggestions, corrections, welcome just trying to get everything in one place for future folks.

Last edited by MCRONI19; 02-26-2013 at 11:16 AM.
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Old 10-14-2013, 09:40 PM
Join Date: Sep 2001
Posts: 86
Has anybody tried this out? I'm thinking of doing this.


Last edited by ssanto; 10-14-2013 at 09:55 PM.
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Old 10-15-2013, 10:10 PM
Join Date: Sep 2001
Posts: 86
I was at the dealership today asking about prices for various things and I got into a conversation with the "accessories guy" about how to add 7 pin wiring and trailer brakes.

He said that there was some wires that needed to be run up under the dash. But this thread only talks about connecting to wires under the hood.

Any thoughts?

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Old 02-08-2014, 02:54 AM
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Join Date: Feb 2014
Posts: 3
Thanks for the great write up! I bought a 2013 F150 XLT today from Hertz with the same issue. Have ordered a Reese Hitch and Curt 4 to 7 pin pigtail. Have you had any follow up or additions since you did the write up? I'll probably add a small transmission cooler and call it good, my trailer is only 3000lbs, but we do a lot of mountain driving.

Last edited by mfmccabe; 02-16-2014 at 01:24 AM. Reason: removed quote
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Old 04-20-2014, 07:18 PM
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Join Date: Jul 2012
Posts: 6
I see that this thread is kinda old but as someone who has done this to their truck I will add my experience. I have an 2012 reg cab STX that came without towing. I purchased the correct wiring harness from ford and replaced everything from the front back. You just remove one harness and put in the new one. I did not have to drop the gas tank. A few of the connections are kinda hard to see but it can be done. My truck was new at the time and I did not want to splice anything.
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Old 07-10-2014, 10:39 PM
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Join Date: Jul 2014
Posts: 2
Just joined after having fixed my TBC problem based on the OP. I can confirm that by splicing and running a couple wires (12v + and brake control), that this does work. Thanks to the OP for this writeup, I now have a working OEM TBC for my 2012 XLT Screw that didn't come with tow package.
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Old 07-15-2014, 06:49 PM
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Join Date: Apr 2009
Location: Fargo, North Dakota
Vehicle: 2006 Ford F150
Posts: 121
This is great news^^^^^did you need to have the computer flashed at a dealer or did it all start working on its own?
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Old 07-21-2014, 07:23 AM
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Join Date: Jul 2014
Posts: 2
Originally Posted by wfburton159 View Post
This is great news^^^^^did you need to have the computer flashed at a dealer or did it all start working on its own?
Yes, you still have to have the dealer flash the computer. There is no workaround for that.
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Old 01-18-2015, 09:26 AM
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Join Date: Jan 2015
Posts: 1
Thanks to everyone for all the great info here. I am looking to do exactly this on my 2014 which is a company truck and I didn't get the choice to order the tow package - so I have to do my own.

I am in the Lucky Category, the connector above the spare tire has the full 7-pin wiring available.

My question is about the 9L3Z15A416A Harness to replace the current 4-wire flat from the spare to the bumper. Is the harness made up of just the tow wiring?

Many images I find on the web when searching that part # show a schematic which includes rear bumper back up sensors... my truck doesn't have rear back up sensors.

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Old 01-18-2015, 10:23 AM
glc glc is offline
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Join Date: Dec 2006
Location: Joplin MO
Vehicle: 2003 Ford F150
Posts: 30,484
You should be able to tie off the leads for the backup sensors.
2003 F-150 XL RCSB 2wd 4.2 M5OD 3.55 LS
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Old 03-26-2015, 12:08 AM
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Join Date: Mar 2015
Posts: 1
I did it!

Bought a new '14 F150 xlt recently. One of those killer deals that I couldn't pass up. Unfortunately, there was no tow package. I installed the 7 pin today and will install the brake controller at a later time. I followed every step in this post and everything appears to be working as it's supposed to be! THANK YOU!
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Old 03-26-2015, 12:08 AM


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