22 trailer brake controller

[varundev]

I joined just for this thread.

I just went through this. I have a 2024 Expedition XLT Max which I bought a bit quickly. My 2016 Expedition engine failed and I needed a tow vehicle. I went out, looked for a newer Expedition, looked for a hitch and 7 pin connector, and bought it. In the 2016, I just needed to install the dash switch and I was good to go. Not so much with the 2024.

I found out I only had the Standard Tow package and figured I needed the switch and maybe a harness and module. The one guy didn't have the brown/white wire and I was missing that from C238 to C214, so I bought the repair kit to add the terminals and some wire to add it to the harness. On the day of install, I took the entire dash apart and came to find out I'm missing ALL the wires needed from the TRM under the dash to the brake switch. Looking in Ford's part catalog, there are more than 30 harnesses available depending on options installed. So, I custom designed a harness, ordered the switch and got everything installed. Using Forscan, I made some changes to enable the brake switch. I was able to get the car to recognize the brake switch and gain settings, but it would not apply power to the 7 pin connector electric brake pin and I was getting a trailer not connected error. So, I ordered the other module, installed it, and everything works. No additional programming at this time, but I know they're are errors in the module based on Forscan output. I have to tow tomorrow and am not taking a chance on bricking a brand new module. I'll try when I get back.

If someone really cares to do all this, I can post part numbers needed and harness design details. It's a very involved task and greatly depends on which instrument panel harness you have.

I'm thinking about making a kit with instructions for those who definitely want the factory installed look. I did not want to hang an aftermarket brake controller in the vehicle.

 

[Mctaf]

Ha - that was the reason I joined. I have a 22 King Ranch with 4WD and after I bought it found out without the HD tow package the 4WD doesn't have the transfer case for 4L - it only has 2W, 4H and 4A. I can't fix that and can live without it but towing my 22' trailer with tractor and 14' enclosed trailer needs trailer brakes! And like you, I don't want to hang an aftermarket part and miss the integration with the OEM system for settings, monitoring, etc.

I can make any mods necessary and would appreciate any information you have on this!

 

[JohnsonEJ23]

I just ran a new LIN wire from the switch to the module last night and it fixed it to where the switch now interacts with the vehicle! A huge thank you to "96s10383"!!! I didn't have a chance to throw a multimeter on the trailer hookup to make sure it's actually doing what it is supposed to be doing, but as long as there are no other missing wires in the factory setup, I'm optimistic this will have been the missing link. I'm traveling for work this week, so I'll have to do that final test after I get back. It's great to now understand that I'm not crazy and wasn't doing something wrong this whole time!

 

[East-TN]

I just ran a new LIN wire from the switch to the module last night and it fixed it to where the switch now interacts with the vehicle! A huge thank you to "96s10383"!!! I didn't have a chance to throw a multimeter on the trailer hookup to make sure it's actually doing what it is supposed to be doing, but as long as there are no other missing wires in the factory setup, I'm optimistic this will have been the missing link. I'm traveling for work this week, so I'll have to do that final test after I get back. It's great to now understand that I'm not crazy and wasn't doing something wrong this whole time!

Are you able to share any pics and info for which pin on the back of the switch and the module you used the jumper wire?

 

[JohnsonEJ23]

Are you able to share any pics and info for which pin on the back of the switch and the module you used the jumper wire?

It's the brown wire on the back of the switch. Tap into that one and then run the new wire to the black plug on the brake controller box under the dash. Pin 10, bottom-left in my photo. If you look closely on the plug, the pin numbers are labeled.

 

[East-TN]

Fantastic. Thanks for sharing, I'm sure this will help a lot of '22 owners.

 

[varundev]

You will need the ML3Z-19H332-J trailer module. There are 2 versions. M and J. Look at your part number on the module and put it into the Ford Parts website. It'll resolve to one of them. Likely, the M version. If not, you'll get the Trailer Not Connected error even if you hook up a trailer and brakes won't work.

 

[JohnsonEJ23]

Just for reference, here is a link I used to reference Forscan info: https://www.f150lightningforum.com/...y-trailer-brake-controller-to-24-flash.25522/

 

[JohnsonEJ23]

I just went out with a multimeter and all of the pins are working as expected! The only thing I'm unsure of is the gain control. When the brake pedal is pushed all of the way in, I'm always seeing a reading of around 6 V. My 11 year old daughter was pushing the pedal for me, so a bit hard to gauge pressure. There were varying readings while she was pushing it about half-way. When the switch's "prongs" were squeezed all of the way together, I got a reading of 12+ volts. I guess I'm not sure how this is supposed to work but kind of figured that the higher the gain control was set the higher voltage I'd read when the brake pedal was pushed all the way in. Does anyone else on here know?

 

[JohnsonEJ23]

So, I just smartened up on two fronts: I remembered I had a multimeter lead extender so I could read the output and push the pedals at the same time, and I realized I could hook it up to my F-150 Lightning (with stock brake controller system) to see how it behaves... After doing so, the expedition with my modifications is working exactly like the F-150 stock. So, I'm finally claiming success on this project!!

But now I'm confused on exactly what this system really does... When I push the brake pedal down all of the way, I get about 6V, regardless of the gain control setting. When the gain control is at 0 or .5, I basically see no change when squeezing the switch on the dash, at a gain setting of 1, I see about 2V when squeezing it and it goes up to 13V when squeezing at a gain of 10, with increasing steps along the way. Again, this works exactly the same on both our Expedition and F-150.

So...does the gain setting not affect the functionality of the brake pedal? Or is it just not doing anything special because it knows a real trailer isn't connected?

 

[JohnsonEJ23]

Ok, so I smartened up again and asked ChatGPT how this works. Looks like it takes info about speed, deceleration rate, ABS status, trailer status (if it detects a load on the trailer brake line) into consideration in addition to the gain setting. So me having the vehicle at rest would definitely impact the Voltage output when pressing the brakes. Squeezing the dash switch, on the other hand, directly controls the trailer brakes with no other logic. Hopefully this helps someone else too. And again, a HUGE thanks to "96s10383" for getting me past my road block of the missing wire in the factory harness... Now I'm curious if anyone has or will run that missing wire from the passenger kick plate area to the module by the foot pedals on the driver side. I'm thinking that the way I did it direct from the dash switch to the module may have circumvented a fuse configuration...

ChatGPT info, for reference:

My input: how does a ford brake controller work from a technical aspect?

Chat GPT Output: Ford’s factory trailer brake controller (often called the TBC or “integrated trailer brake controller”) is more sophisticated than a simple dash-mounted aftermarket controller. Here’s how it works technically:

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1. Inputs & Sensing​

• Brake Pedal Position Sensor
  Instead of just watching for brake light power, the TBC reads the brake pedal position sensor (BPPS) on the truck. This gives it a proportional signal of how hard you are pressing the brake pedal.
• Truck Speed & ABS Data
  The controller is tied into the ABS module (and sometimes the yaw/traction system). This way it knows actual vehicle speed and wheel slip, so it won’t apply too much trailer braking at very low speeds or when wheels might lock.
• Manual Override Lever
  The dash slider/lever lets the driver command trailer brakes independently of the truck brakes (useful for trailer sway control or testing).

---

2. Processing (How it Decides Brake Output)​

• The brake controller is integrated into the truck’s body control / ABS network via CAN bus.
• It looks at:
  • Pedal force (from BPPS).
  • Vehicle deceleration (from ABS sensors).
  • Gain setting (driver’s adjustment in the dash menu).
• Using these, the controller calculates the desired trailer brake current (how strong the magnetic brakes on the trailer should pull).
• Some Ford models also blend in sway control logic—if the yaw sensors detect trailer sway, the TBC will pulse the trailer brakes to help straighten it out.

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3. Output (How Braking Force Gets to the Trailer)​

• 7-Pin Connector, Brake Output Pin
  The TBC sends a modulated DC current on the trailer brake wire (blue wire, pin 2).
• The signal isn’t just on/off—it’s a smooth ramped voltage/current, typically 0–12V at up to 20–25A, depending on trailer brake coil resistance and number of axles.
• It uses a solid-state transistor (MOSFET) power stage, not a mechanical relay, so the output is pulse-width modulated (PWM) and precise.

---

4. Feedback & Safety​

• Current Sensing
  The TBC measures actual current flow to the trailer brakes. If it doesn’t detect current when it should, you’ll see “Trailer Not Connected.”
• Fault Detection
  Short circuits, open circuits, or overload conditions will trigger warnings and shut down output to protect the truck’s wiring.
• Proportional Behavior
  Because it measures pedal pressure and speed, the braking force scales naturally. Light braking = low trailer current, hard braking = high trailer current.

---

5. Extra Functions​

• Hill Start Assist & Tow/Haul Mode
  In Tow/Haul, Ford adjusts the brake gain curves for heavier loads.
• Trailer Sway Control
  Uses the trailer brakes selectively to counteract oscillation.
• Integration with ABS
  Unlike standalone controllers, Ford’s system won’t allow the trailer brakes to apply more aggressively than the truck can handle without wheel lockup.

---

In short: The Ford integrated brake controller is an electronically controlled current driver that uses brake pedal sensors, ABS data, and CAN integration to send proportional, PWM-controlled current to trailer brake magnets through the 7-pin connector, with safety monitoring and diagnostic feedback.

 

[East-TN]

Excellent info.

 

[Langer]

It's the brown wire on the back of the switch. Tap into that one and then run the new wire to the black plug on the brake controller box under the dash. Pin 10, bottom-left in my photo. If you look closely on the plug, the pin numbers are labeled.

So to confirm, you did not have to tear the dash apart for this, you just added the LIN jumper from brake controller box to the switch?

 

[JohnsonEJ23]

So to confirm, you did not have to tear the dash apart for this, you just added the LIN jumper from brake controller box to the switch?

That's what I did, yes. I scraped a bit of the wire coating off on the LIN wire coming out of the "squeeze switch" and soldered wire to it with some heat shrink around it. I put a Molex pin on the other end of the wire and installed it into the black Molex going into the controller by the pedals. BUT now I'm questioning if that was really the best way to go about it. By design, I believe it was supposed to run to some connector by the passenger kick panel and then back over to the brake controller by the driver pedals. I don't have a full wire schematic, but I'm wondering if that was supposed to be fused and if my running that wire direct, if it's bypassing having a fuse. Does anyone have the full wire schematic that they could reference?

 

[Mctaf]

Wiring diagram with Trailer Sw

 

[Mctaf]

Page file

 

[JohnsonEJ23]

Thanks for posting! I'm not used to reading these. How do we figure out where C238 and C214 are and what they look like?

 

[East-TN]

In the back of the Service Manual it will show the locations of the wire harness and the connectors. Here is an image for the 18-21 I took a screen grab for...maybe someone with the '22 will help you.

 

[Mr Big]

Your definition of the voltage appears to be correct. The system is electric and based on resistance. The harder you push the more voltage is applied causing the magnets on the trailer to work harder. There is always an adjustment on the controller for intensity. I can cause my empty 8x16 dual axle trailer to lock up the tires. So, I adjust for the load. I turn down the resistance for light load and up for heavy load.
To test, with the trailer attached and rolling around 10 to 15mph, I squeeze the prongs without applying the brakes. If the trailer skids, I lower the setting. If it doesn't slow down much, I raise it until it slows down and stops the movement similar to rolling up to a stop sign.

 

[Mctaf]

From a 2022 KR with Class IV Tow Prep Pak and not HD Tow Pkg. C238 is brown - behind control switch in dash. - that's what the switch pig tail plugs into. C214 is Gray in passenger floor side kick panel also shown to the right of fuses slightly hidden.

You can see brown white wire in top of C214 that goes to C238. The bottom does not have the wire (pin 5) - that's what would connect to the controller by the steering column. The diagram does not show any additional connections so the purpose of this brown/white wire is to connect the control switch to the controller. I'm going to do what JohnsonEJ23 said, splice into the switch brown/white in the dash and connect to the controller about 3' away rather than picking it up in C238 and routing it across to the other side behind the dash.