"Trailer Brake Module Fault" Message Won't Go Away

[Rah150]

Happened to me today. 23 PB. Pulled out 91 fuse looked fine put it back in. Error and fast turn signal went away. Also pushed in a lot of the fuses which did seem not fully set.

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[Eck]

Same happened to me with error code and rapid blinkers- thanks everyone for all of the info on this thread as I just pulled all fuses in the diagram Smitdog posted and reseated them- code went away on restart.

 

[Blackhawk36]

I had this happen last week after hooking my old trailer up.
fast blink. Module fault warning on start. Also had no out put to trailer lights after it started.
i pulled the fuses i saw that said tow.
i kept updating this thread for new info.
Unplugged battery this morning.
everything still has power with the hybrid ??‍
Then i noticed the fuses at the top of thread.
i hadn’t seen #91 fuse.
i pulled it and it was blown.
i put a 20amp fuse from the aux port in there and all is back to normal.
I’m so glad. So i registered to let y’all know.

I had the exact same problem and the #91 fuse was blown. Changed and all good. My boat trailer is put into salt water a few times a year. One of my clearance lights corroded internally and shorted to ground. Trailer rewire is now on my list.

 

[kman7799]

I bought a 2023 Powerboost in February this year. I had the trailer brake module fault and fast turn signal happen after an OTA update in March. The module fault would only appear when I started the truck. I brought it to a dealer who told me the OTA update failed and caused the trailer brake module to fail. They updated the software manually and replaced the brake module.

Since then I've had a brake module fault appear twice, oddly when I was turning a corner. Tonight I received another OTA update and the same brake module fault and fast turn signal happened again. I removed and readded fuse #91. After that I started the truck. The fault didn't appear and fast turn signal went away. Thank you for posting that info!!!

I turned off automatic software updates. Now to test the brakes and lights on my trailer. Anyone else seeing this after an OTA update?

 

[Thor’s Stormboost]

I pulled 42 and 91 just now, both weren’t broken but did have a slight bronzing to the fusing element. I also was able to push down and seat most fuses in there better. Still have the trailer brake fault message on accessory, then start up for a second and then goes away. I know I’ve seen an option for this SSM 52466
2021-2023 F-150 - Trailer Brake System Fault See Manual
Message In The IPC With Diagnostic Trouble Codes (DTCs) B1D08 And/Or
B1D09 In The TRM. I’m hoping to avoid going to the dealer if I can fix it myself but the only thing I have left is to check the trailer tow connector.
anybody have other fixes for this?


update: replaced Fuse #42 and #91, problem solved. Message went away

 

[Bassman]

Thanks for this tip. I had the same problem and took it to the dealer and got the same story. Bad module and on extended backorder. Saw this post thread and pulled fuse #91 and waited a few minutes and reinstalled it and issue went away. Smitdog, thanks for posting the fuse box and highlighting the fuse locations. Very helpful. Thanks again!

 

[CB75]

I connected a boat trailer that had some really old / frayed wiring. Connected trailer's 5-way into truck's 7-way adapter, all worked fine initially. Eventually trailer wiring frayed off completely or shorted out, and I received a "Trailer Brake Module Fault" message on the dash.

No big deal, or so I thought. Disconnect trailer, and hit "OK" on message. Didn't work. For the past week I get the error message everytime I start the truck. Also of note, I have a "fast" blinker indicator sound, but all blikers are flashing at normal speed.

In an effort to clear the message, I went so far as to delete the associated trailer profile, checked all fuses related to a trailer (highlighted in red), and disconnected the battery for 10 minutes. Still get the error message and fast blinker sound.

I've read on other forums that disconnecting the battery for 20+ minutes has cleared the fault. I disconnected for 10 minutes, thinking that should be sufficient... But perhaps not long of enough time?

Any ideas? Seems like it would be a simple process to reset / clear.

#42 Trailer brake control module
#55 Trailer tow park lamps
#56 Trailer tow stop and turn lamps
#58 Trailer tow backup lamps
#91 Trailer tow light module
#107 Trailer tow battery charge.

This was super helpful. I also had a "trailer brake module fault" and fast turn signal indicator blinking. I pulled each of these fuses and inspected them. I did not find a blown fuse, but some of them were not well seated in their sockets. After pulling all of the above fuses and replacing them snuggly in their sockets, everything is working appropriately again. I don't know if pulling them out and replacing them reset something or if one of them was just loose. Thanks for the help, though!

 

[natefons]

for anyone else having the same issue ( i had it too)

I took all the red highlited out and re-seated them. issue went away.

the fuses were different than the ones i have used elsewhere (on my boat for example).

 

[fitifiti]

I had the same issue with the error code and fast blinkers. Thanks to this thread, I pulled and reseated the fuse #91 from Smitdog’s diagram—problem solved on restart!

 

[John Tera]

Hi all
I have the same problem on my 2024 PB “Trailer brake module fault” and “trailer wiring fault”
I checked all the fuses and they are good, I tried to fix them good since they come loose from the factory and I have checked fuse 91, 42, 34 but the problem stayed on.
I have no blinker problem it is working fine. I brought a technician with OBD tester and he couldn’t find the source for that issue. Appreciate your advice, thanks.

 

[Cobraman428]

Hi all
I have the same problem on my 2024 PB “Trailer brake module fault” and “trailer wiring fault”
I checked all the fuses and they are good, I tried to fix them good since they come loose from the factory and I have checked fuse 91, 42, 34 but the problem stayed on.
I have no blinker problem it is working fine. I brought a technician with OBD tester and he couldn’t find the source for that issue. Appreciate your advice, thanks.

I took my 2021 PB truck for service at the dealership 3 years ago and when the tech got out of truck he hit a connector near the brake pedal with his boot. I got in and had trailer fault displayed. He said that caused my Trailer brake fault issue. He reach under the dash and pushed the connector and fault went away. Not saying this is your issue, but you asked for suggestions..

 

[Illudium_Q-36]

BCM TCM



2023 Ford F-150 XLT Package



My experience (for information purposes only—proceed at your own risk).



The Trailer Brake System Fault message would appear at random while driving, but it always appeared immediately when pressing the brake pedal. My OBD2 reader showed codes B1D08 and B1D09, which indicate left-hand and right-hand trailer direction short circuits to ground. I reset the module but the fault message reappeared.



With the battery disconnected, I checked resistance to ground for the left and right turn signal lines on the 7-pin socket. Both measured around 40kΩ (40,000 ohms) to ground—hardly a short.



When I connected a tester to the 7-pin trailer socket, all LEDs illuminated as expected—except when activating the turn signals. Activating the left turn signal caused the right signal on the tester to glow faintly, and vice versa. No related fuses were blown, and there was no actual short to ground, so I began to suspect a software glitch and erroneous OBD2 codes.



⸻



BCM / TTM (Trailer Tow Module)



The BCM (Body Control Module) sends control signals to the TTM (Trailer Tow Module)—also called the TCM (Trailer Control Module)—which manages taillights, turn/brake signals, reverse lights, and auxiliary 12V on the 7-way socket and 4-way plug.



The TTM is mounted inside the cab, behind the dash to the left of the steering column. It has two connectors. To remove it, press down the plastic tab and slide the module off its metal bracket—no need to remove the bracket itself.



Inside, the TTM circuit board contains surface-mount components, a single relay, and a large electrolytic capacitor. I don’t recommend opening the TTM, but for troubleshooting I removed mine for about 45 minutes. After reinstalling it, the Trailer Brake System Faultmessage has not reappeared in over two weeks.



⸻



My Theory



My working theory: during the 45 minutes the TTM was disconnected, the capacitor fully discharged, effectively resetting the module’s software. Like most electronics, these systems can glitch. When errors occur in onboard memory or the microprocessor, the first troubleshooting step is often the same as with any electronic device—restart it.

 

[OneMore]

BCM TCM



2023 Ford F-150 XLT Package



My experience (for information purposes only—proceed at your own risk).



The Trailer Brake System Fault message would appear at random while driving, but it always appeared immediately when pressing the brake pedal. My OBD2 reader showed codes B1D08 and B1D09, which indicate left-hand and right-hand trailer direction short circuits to ground. I reset the module but the fault message reappeared.



With the battery disconnected, I checked resistance to ground for the left and right turn signal lines on the 7-pin socket. Both measured around 40kΩ (40,000 ohms) to ground—hardly a short.



When I connected a tester to the 7-pin trailer socket, all LEDs illuminated as expected—except when activating the turn signals. Activating the left turn signal caused the right signal on the tester to glow faintly, and vice versa. No related fuses were blown, and there was no actual short to ground, so I began to suspect a software glitch and erroneous OBD2 codes.



⸻



BCM / TTM (Trailer Tow Module)



The BCM (Body Control Module) sends control signals to the TTM (Trailer Tow Module)—also called the TCM (Trailer Control Module)—which manages taillights, turn/brake signals, reverse lights, and auxiliary 12V on the 7-way socket and 4-way plug.



The TTM is mounted inside the cab, behind the dash to the left of the steering column. It has two connectors. To remove it, press down the plastic tab and slide the module off its metal bracket—no need to remove the bracket itself.



Inside, the TTM circuit board contains surface-mount components, a single relay, and a large electrolytic capacitor. I don’t recommend opening the TTM, but for troubleshooting I removed mine for about 45 minutes. After reinstalling it, the Trailer Brake System Faultmessage has not reappeared in over two weeks.



⸻



My Theory



My working theory: during the 45 minutes the TTM was disconnected, the capacitor fully discharged, effectively resetting the module’s software. Like most electronics, these systems can glitch. When errors occur in onboard memory or the microprocessor, the first troubleshooting step is often the same as with any electronic device—restart it.

Thank you for your investigation that suggests another source to examine.
My 22 PB started showing the TB fault last week.
Found this thread discussing this issue with possible fixes. I'll be looking into correcting this tomorrow.

A big thank you to everyone that contributed.

 

[OneMore]

This morning I replaced 30 amp fuse in location, 91.
No more fault warning or hyper flash.
In my case the fuse had failed. Don't know why it failed.
31k and three years of use. Never towed anything.
I too found many of the fuses not seated fully.

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