These new vehicles have a constant drain on them. they have internal clocks, plus they "listen" for the remote, there has to be active circuits for the unlock/lock auto start, etc to work.

 

Reviving the thread to post some battery numbers in case anyone is curious.

So to confirm, on the OP, it was definitely battery voltage that kept auto stop from working. As a test I had let the truck sit for a few days, plus it's been hitting the freezing mark here. Took the truck out a couple of days ago and this time actually saw the "battery charging" message on the autostop status screen when I was stopped and auto stop was not active (when autostop is active the message reads "engine stopped").

Driving around town for an hour or so that day never got the battery back up to a point where autostop would kick in. Yesterday I did a 100 mile round trip, mostly freeway. At my destination city, the battery was still not charged enough for autostop to activate. By the time I got back to town, it just started working two stops before the house.

When I got home, I tested the battery voltage and it was 11.75v, so that looks to be about the minimum voltage for autostop to kick in. Just to doublecheck max battery voltage, I threw it on the charger and at full charge the battery was at 12.99v. That's for whatever battery they put in the '16 2.7XLT. Don't know if different packages have different batteries or not.

Anyway, thought some might be interested in the minimum voltage for autostop. On a side note, it appears there's a decent amount of "idle drain" on the battery when the truck is just sitting.

 

Very interesting! I'm hopeful did not make the "idle drain" more than it should be. Not everyone drives their truck everyday. Hmmm?


biz

 

What I am learning is that the newer the truck, the more likely additional conditions/parameters there are to prevent the Auto Stop/Start (***) from working. My info screen always says Engine on due to the temperature setting (can't recall the exact wording). In my case I have read about 15+ conditions that tell the computer in my 2021 F150 to not use ***. So when mine stopped working after about 3 weeks I reviewed this list. Turns out the front window defroster is on in. So I started thinking about this and understand why if you are trying to defrost your windows this would defeat it. But it's been nice weather here in Calgary for fall so why is this happening in a 2 month old truck with neither the AC nor the defroster on? Then it hit me—maybe the way the computer senses the defroster is on has nothing to do with the temperature of the air—but with the selection of the vent direction. So I went into the settings on screen for the vent and sure enough, it was set to the windscreen. As soon as I turned it direct the vent air to the passenger (mid range) setting, *** started working again.

Happy happy.

 

Dealer tells me the stop/start quits working below the 80% charged threshold. I have a '21 3.5. I have also had issues with the rear auto braking function and the drivers side back-up sensor. I charged up the battery and the issues stopped. Ford replaced the battery about a year ago as they did find an issue with it but the real issue appears to be the alternator does not fully charge the the battery unless you drive a lot of miles...which I find ridiculous. They probably have too much stuff running off the alternator keeping it from fully charging the battery. I have an outboard motor that has an alternator with 50 dedicated amps for the starting battery and the remaining 80 amps for running the electronics. And yes, it has a 130 Amp alternator. The fact that I have had issues with the back-up sensors and the cross traffic rear braking makes this a safety issue. So the dealer says to put a battery minder on it and plug it in...If I wanted a plug-in truck, I would have bought in an EV. If Ford thinks we should have battery minders in the trucks, they should be responsible for installing them. This is nothing more than a manufacturing defect...bad planning on charging the battery.

 

Just unplug the BMS on the negative cable or use Forscan to disable it. Then you will get constant charging. The advantage to unplugging the BMS is that you can plug it in on long trips to take some strain off the alternator and get you a few extra miles per tank.

 

Thanks. Might just try that. Also, Thanks for your service. Was in 1st Brigade, Ist Inf. '67-'68 RVN. Located at Phouc Vinh, then Quan Loi. Rotated home Feb.'68 (Tet Offensive)

 

Thank you as well! Desert Shield/Storm/Calm here. Man 1st ID had it rough during Tet. My battalion, 716 MP, had a Presidential Unit Citation from that. Lot's of history on the walls of the old battalion HQ there at Ft Riley.