Anti-lock Brake Fault - battery issue?

[CarbonGrayBronco]

Got a weird issue with my Bronco (2024, 10k+ miles, 2.7) after disconnecting the battery. I was installing a dashcam and disconnected the battery while installing. The battery was disconnected for a few days and I got an alert my Bronco was going into battery saver mode. Re-connected the battery, started it up, and got an anti-lock brake system fault. Turned the Bronco off and re-started…no errors or lights. Drove around without issue for a couple weeks.

Had to disconnect the battery again a week later and days after I start it up and get the same light. Again I turn it off and back on and the light eventually clears and I drive without issue. Battery voltage was about 12.9v on the dash info screen. Took it to Advance and their reader said the battery was fine, alternator was fine.

I really doubt it’s actually the brake system since it’s happened twice and only after the battery was disconnected.

Any ideas? I’m still leaning towards this being a battery-related issue.

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[Brian_B]

To start - the battery voltage you see on the dashboard while running really only tells you if your alternator is working or not. So doesn't really say anything about the battery (although there are ways to infer such, it's not straightforward)

I'd try this (I know you've done some of this already though, but doesn't hurt anything)

General Reset for Wierdness
Unplug the negative battery terminal for about 5 minutes
Reconnect the negative terminal
This reboots all the modules and computers in the Bronco
Use a trickle charger rated for AGM batteries:
Connect (+) to the (+) battery terminal
Connect (-) to either chassis ground or the side tab on the (-) battery terminal
DO NOT connect directly to the (-) battery post
The BMS system must see the charger and going directly to the (-) battery post will bypass it.
Let the battery trickle charge over night. Low battery voltage, or just the BMS thinking there is low battery voltage, can cause a lot of odd things to occur and this corrects for that possibility.

 

[GA2Dr]

For what it's worth I have no issues with my battery. Every time I've disconnected the battery I've gotten a brake fault light on the dash. It goes away after a little bit of driving. I've checked it with Forscan each time and it's the same one - I can't remember the exact code but I believe it's communication failure with the brake module or something to that effect. My take: if it is only connected with a battery disconnect I would not worry about it unless you have other symptoms.

P.S. mine is a '24 with about 22k miles.

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