Question about modem/battery issues

[LibDan]

My new truck (under 500 miles) is having an issue that is about to send it back to the dealership's service department. (But not until Feb. 27th apparently. )

The issue began a couple days after I brought it home - I wasn't able to remote start, lock, unlock, or locate the vehicle. The FordPass app just spun for a while and then finally told me it "failed." I fiddled with the vehicle settings in the garage that night, resetting vehicle auto updates, remote start, and all connectivity settings. The app found the vehicle again... for a little over two days. Then it stopped working again (this would have been last Thursday evening). I tried rebooting my phone and toggling my settings again, but nothing helped. It kept not working until 7:30 PM Saturday when it suddenly started working again. It has not stopped working since then (and today is the following Tuesday.)

Meanwhile, as I was trying to troubleshoot this issue myself, I logged into my vehicle dashboard on the Ford page and noticed this:

I wondered what service it could possible need at then under 300 miles. But the dashboard doesn't tell you what service it needs or why it think it needs it. So, I used the chat function to talk to Ford and the chat rep was able to tell me that their system was showing that, "Invalid Data Received From Anti-Lock Brake System (ABS) Control Module)." They suggested taking it to a Ford dealer and talking to the folks at FordPass.

I called FordPass because this was Saturday and the Dealer service dept. wasn't open. The FordPass rep verified that I had multiple failed (timed out) attempts to do things with my truck. We verified that it should work fine on my phone and that my phone software was up to date. We verified that the truck software was up to date. We reset the truck settings again. Nothing worked. The FordPass person told me to take it to a dealership and tell them that, "The modem is not connecting."

I tried contacting the dealership yesterday, but no one got back to me. I tried again today a bit more determinedly and finally got to talk to a service advisor. Before I was even three sentences into explaining the sequence of issues, he starts trying to suggest that the problem is my phone. I told him that FordPass said my phone should work fine and that I had the most up-to-date software. When I got to the bit about invalid data from the ABS, he told me that this was a "U-Code" which meant it was a battery issue. He wants to run a battery test, but not until February 27th.

Now, I know that the Mavs have historically had some battery issues, but the 2025's have an upgraded battery from what I've been reading. I've also seen a bunch of other people on here having FordPass issues. And FordPass is telling me that the modem is not communicating.

So, does this make any sense to anyone else who knows something about these systems. Does a battery issue cause problems with the ABS and FordPass but seems to cause no other issue, seem like a reasonable answer? Could it be a problem with the CAN bus system instead? Or simply a faulty modem?

Thanks.

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[HeyBales]

Could be faulty modem, TCU - be glad your issue with it isn't as a couple others had discovered - faulty and draining the battery overnight.

But - the modem must connect to ATT network - how is that signal strength in areas you park it?
(if you don't use ATT, the 3 carriers usually share towers and have similar coverage - if your say T-Mobile sucks, well, ATT probably does too)
When you park - it sends up some data you can see in app, location, tire pressure, OLM, ect.
Sends other data too Ford has access to.

Battery being low affecting only ABS and not other things that would be reported on - I'm betting not. That sounds like bad troubleshooting.

Considering how systems interact - I could even see your account on Ford server having some bad data in it, causing connection or communication issues for both the app side of it, and the truck side of it.
But if the techs said they didn't see your truck modem connecting at all - I'd trust that as pretty easy for them to see.

The fact that it could connect at all means it's not like bad SIM info in the modem, it's intermittent mostly not working, so wiring, or software issues using it.