2014 Ford Expedition XL Adding Third Row

[k-bl]

I have not seen this conversion, but I have seen interest in it, so I thought I'd go ahead and post it online.

I purchased an ELECTRIC third row, wiring harness, belts, buttons, and interior moldings for my 2014 Expedition that doesn't have a third row. You can read about the purchase here: https://www.expeditionforum.com/thr...tion-did-i-get-a-good-deal.45476/#post-414843.

I'm an engineer by trade, and have worked on Ford's since I was young, so a little splicing and dicing doesn't put me off. Anyway, I started the arduous process of first replacing the wiring harness (it connects up to the fuel pump, break lights, and I believe rear AC condenser unit). I can get pictures tomorrow. But I'm curious, what extra power would need to be ran to where the seats connect into the rest of the harness (the BIG WHITE plug on the driver's side)?

I connected one of the seats up after retro fitting the new harness in place and testing the break lights, and fuel pump. It, of course, didn't move. So perhaps I need to add in power from the fusebox to it?

Does anyone have a wiring diagram perhaps? I can't wait to post pictures, but I am beat from removing panels, removing wiring left from its past life as a Fire Station RV, and lifting those new seats.

Fun times ahead!

 

[Plati]

I have a 2014EL .... could look and take a pic possibly ... if that helped.
I removed the driver side 2/3 seat ... have it stored for now. 1/3 seat still operational.
You have that setup?
Maybe all you need is a fuse installed?
MrTexasJoe is doing the same deal (different year) ... I think

 

[k-bl]

Ok, I started big, and starting putting in the ENTIRE donor wiring harness (beside the original, just to see how it worked). However, there were a few plugs that didn't connect to anything, and I got all the way to the lift gate. I had started on the passenger side, where the relays are, and the wiring harness was so large, it went clear to the other side.

The lift gate had a single plug that was not correct, and the lift gate wouldn't operate entirely. To keep progressing, I then started looking at wiring diagrams to see if we could ensure wiring actually even made it back to the seats.

Going even simpler, I then found the specific wires that go to the third row seat from the breaker box, and after a few iterations, just the actual wires that go to the third row power seat now added specifically to the connectors on the passenger side starting at the pillar back to, and now in, the relay box along with the relays. The seats still don't work, the relays don't seem to fire. Next, later this week, I'll probably have to start using a power meter to see where voltage is missing.

It feels like I'm close.

 

[k-bl]

Documenting "where I'm at", to help future third seat enthusiasts...

Wiring diagram starting at the "RH C-pillar":


Here is the pinout for the power side's C410 plug. This is where the seats get their power apparently. Pin 3 is of special importance:



Pin 3 was empty on the male side, but has a cable on the female side. I believe this means that the connection from under the hood, fuse number 70, connects here. So, starting from the power cables you can see the new brown and red addition (C410, located at RH C-pillar, 3 SBB70 BN-RD 12 FUSE - 70 OR CIRCUIT BREAKER 14A005 1) which I swapped from donor wiring harness:


The next we'll follow the brown and red wire to the "Auxiliary Relay Box 2":


In my vehicle, the "Quarter Window Close Relay", "Quarter Window Open Relay", and "Auxiliary Blower Motor Relay 1" were populated. All other relays were empty. So I as well transplanted the "Third Row Power-Fold Seat Relay" into the "Auxiliary Relay Box 2". Here is a view from the top (this is in the interior loading area near the passenger side tail light), with it still open:


Continuing because I've reached limit of uploads in next forum post.

 

[k-bl]

And of course, the newly added brown and red in from the donor wiring harness (pink out goes to the switches):


Then the ground side of things (wire nut, don't judge me, I'll solder it later) on the other side of switches:


And of course, to the frame:


So that covers the power side. Next (with repeat picture of the "Auxiliary Relay Box 2" for logical flow) I'll cover the control side.

Continuing because I've reached limit of uploads in next forum post.

 

[k-bl]

Starting again at the "RH C-pillar" (repeat picture from https://www.expeditionforum.com/threads/2014-ford-expedition-xl-adding-third-row.45623/#post-416496):


We have the pinout of the C411 plug. This is where the seats get the control apparently. Pin 20 is of special importance:


Pin 20 was empty on the male side, but has a cable on the female side. I believe this means that the connection from the passenger side fuse box connects here. So, starting from the control cables you can see the new blue addition (20 CPS48 BU 20 CTRL MOD. - RELAY(S) 3RD ROW SEAT 1) which I swapped from donor wiring harness:


This connects as well to the "Auxiliary Relay Box 2" (almost repeat image from https://www.expeditionforum.com/threads/2014-ford-expedition-xl-adding-third-row.45623/#post-416497 for continuity):


The green and black goes to ground (again with the wiring nut from https://www.expeditionforum.com/threads/2014-ford-expedition-xl-adding-third-row.45623/#post-416497 for continuity):


Continuing because I've reached limit of uploads in next forum post.

 

[k-bl]

Here we attach again to the frame (repeat from https://www.expeditionforum.com/threads/2014-ford-expedition-xl-adding-third-row.45623/#post-416497, for continuity):


So I guess next I need to examine the Smart Junction Box in the passenger compartment, and the Battery Junction Box in the engine bay?

 

[Trainmaster]

Looks like you have the wiring diagrams you need.

I've done lots of upgrading to XLs and XLT's but never worked with the seats.

Ford appears to have no less than two sets of wire harnesses; one for XLT trim and one for premium trim. Remember that if a plug or jack doesn't have a wire going to it in an application, the contact inside it is missing too. So don't expect to plug something in and it works. You can add the pins from a donor plug. Same with the fuse box. Some empty locations have no metal contacts in them. Some do.

You have to spend lots of time with those diagrams and pin layouts and a test light to figure this all out. If it were me, I would probably only have run a new hot lead to the seats, if that did the job and not swap the entire harness. But either way would work; decoding the harness and its plugs is just a bit of work A good dependable test light is your friend.

 

[k-bl]

Looks like you have the wiring diagrams you need.

I've done lots of upgrading to XLs and XLT's but never worked with the seats.

Ford appears to have no less than two sets of wire harnesses; one for XLT trim and one for premium trim. Remember that if a plug or jack doesn't have a wire going to it in an application, the contact inside it is missing too. So don't expect to plug something in and it works. You can add the pins from a donor plug. Same with the fuse box. Some empty locations have no metal contacts in them. Some do.

You have to spend lots of time with those diagrams and pin layouts and a test light to figure this all out. If it were me, I would probably only have run a new hot lead to the seats, if that did the job and not swap the entire harness. But either way would work; decoding the harness and its plugs is just a bit of work A good dependable test light is your friend.

TY for your reply! I took the plugs apart on the donor wiring harness, and used a paper clip to bring the wire and contact/pin out and inserted it into the existing harness. So that part should be sound. I'll start with a voltage meter next, testing wire by wire back to the back. I also need to test the motors on the seats as well. A small thing, but I think listing it here as something that needs done will help future novice installers.

 

[k-bl]

I found a debugging guide and went through each step. I was able to test voltage all the way back to the power cable, and I'm getting over 12 volts to the ground. I then tested the control wire from the passenger side fuse box, and I have essentially no resistance. Fuses are all where they should be, it looks like it may be part of the circuit board simply isn't there to tell the rear seats to be able to work when a door is open and the car is in park.

 

[John Kohler]

This is a long shot, but my power seats will not operate if the rear hatch is open and the doors are locked.

 

[Trainmaster]

Good to see you've got the connector pins figured out.

If all else fails, and you don't want to mess around with re-discovering and installing any computerized door-open-interlock logic circuitry designed into this thing, you may have to just find the power lead and wire it to an unused fuse.

If you really want to stretch your sills, you can learn about Forscan and see if the optional logic can be programmed into the truck's computer. I have no idea how Ford interlocks the seats, but Forscan's spreadsheets posted on the Internet would be one place to explore.

It's a long shot, because Ford's documentation of optional accessories is somewhat sketchy, but the shop manual may discuss the logic in any pinpoint diagnostic charts provided for troubleshooting the seats.

My how things have changed!

 

[k-bl]

it looks like it may be part of the circuit board simply isn't there to tell the rear seats to be able to work when a door is open and the car is in park

I think the circuit board is fine, I checked the part number, 7L1T14B476A, and it is used on other Expeditions with a third row. I'm thinking more and more this is a computer issue that needs to be adjusted either by resetting the SJB (smart junction box, passenger side fuse box) or adding it via FORScan.

 

[Trainmaster]

Keep us advised. Interesting stuff.

 

[k-bl]

So I brought it to the dealer, explained my situation, and they at first didn't really know what to do. So the service manager was called over, and I explained again, he basically said it isn't a module you can turn on or off, and that Ford themselves would control most of the codes, but he was very curious about the vehicle, and decided to grab a computer, hook it up and see what he could do. This is him on the computer, after it first getting connected:


He went through, and didn't see anything of note that included the third row. He started to disconnect everything, and I asked: "What if we just reboot (not a reboot, like disconnect the battery, but a reset of the computer itself, and its memory) the SJB/GEM?" He said that would be fine, warned me of the risks, but reconnected, and did that. I heard the SJB make all sorts of clicking noises (relays), and this is EXACTLY what I wanted to hear. We opened the rear hatch, to see if that did the job...


AND IT DID!

Here the manager is, (he had just given me a thumbs up, and I got permission to post his photo):


Here is the guy I first talked to, that got the manager involved, after I told him we just did something never before done on an Expedition (just after I got his permission to post his photo):




An hour later, after buttoning up the wiring, here is the install before reassembly and install of the seats:



Continuing because I've reached limit of uploads in next forum post.

 

[k-bl]

Now to fix a few wiring issues from its former life of a Fire Station vehicle, and seats will be going in. I will probably not document the seats being installed, because that part is the same with or without the third row. In the end, I asked the manager what exactly he did, and he said:

"I cleared the KAM (keep alive memory), cleared codes in the SJB (smart junction box)/GEM, and ran the self test just on the SJB which cased the relays to click."

I hope this helps future "third row enthusiasts".

 

[Trainmaster]

Sounds like when rebooting, it recognized the module. Well that's interesting.

 

[star-art]

The SJB enables and disables the relay for the 3rd Row Power-Fold Seats. There's also a Liftgate/Trunk Module (LTM) for vehicles with Power Liftgate, but since he got his to work without retrofitting that (unless I missed something), it tells us serial communication between the SJB and LTM apparently isn't needed for this to work.

It's quite possible the 3rd Row Seat Enable FET on pin 24 of C2280C of the SJB has to enabled in firmware. Apparently the reset done by the dealer somehow accomplished this.

At any rate, I'm glad to hear you got it working!!! For anyone else reading this thread and thinking about doing this, here's some additional info that might help:

There are two different control setups for the 3rd Row Power-Fold Seats. These controls are not swappable or compatible since the Body Control Module in 2015-17 was programmed differently than the SJB from 2007-14.

In all years, the 3rd Row Power seats were paired with the Power Liftgate feature.

The seats will operate only if the vehicle is in Park and the rear liftgate is open. This is to help prevent any mishaps where the seat might move with someone sitting in it. (It's no guarantee, but that's what Ford came up with.) If you retrofit 3rd row power seats into your vehicle, for safety as well as liability reasons be sure to wire it up to factory specs and don't try to bypass the SJB/BCM control of the relay.

Since you got yours to work with (what I'm assuming is) a standard liftgate, that tells me the SJB is looking at the decklid ajar input as well as the transmission status to determine whether to enable the 3rd Row Power-Fold Seat Relay. Thankfully, 2007-14 vehicles with a Liftgate Module (LTM) have a dedicated output for Decklid Ajar. This is what made it possible for you to retrofit 3rd Row Power-Fold Seats without also adding the Power Liftgate feature at the same time.

For 2007-14, you press and hold the switch to move the seats. Starting in 2015, this entire setup changed and the switches became momentary where one brief press in either direction moves the seats all the way open or closed. This means the 2015-17 BCM is programmed completely differently. It also means newer style switches won't work in older vehicles without adding some custom electronics.

Hope that helps!

 

[k-bl]

Tested the seats out again last night, and it seems the computer has reverted back to the original behavior. Not sure what to do at this point, so calling Ford customer service to see if they can do anything.

 

[star-art]

The SJB *should* be the same for all models as that would save Ford money over making dedicated hardware so it makes logical sense. The SJB has some computer firmware in it that allows for configuring different options.

If it can't be re-flashed for any reason, you might be able to swap your SJB with one from a Limited or King Ranch. These models had the 3rd Row Power-Fold as standard.

But, before doing anything else, you need to get a factory service manual (FSM). It will contain detailed diagnostic instructions for chasing down problems with the Power-Fold setup.