My sons 2021 Bronco went into "deep sleep" mode. It starts easily and runs fine, but doesn't seem to want to come back into a normal mode. He took it to a parts house and they told him he needed a new battery. He has ZERO indications the battery is weak. Anyone else having this problem?

 

A new battery is one option, and a reasonable step. Or you could put a battery maintainer on it overnight and see if that helps. Either way, it's a good idea to reset the battery management system (BMS). I don't remember the procedure to force a reset, but ti should relearn if the vehicle sits overnight for over 8 hours without being touched. Actually a battery mainteiner isn't a bad idea for most vehicles these days. It takes longer drives than people realize to full charge the battery, over 45 minutes at least once per week. Notice I say battrey "maintainer" not "charger. make sure it's one of the modern muti-step units like Noco or Ctek, because those won't damage your battery if you leave it connected for days or longer.

Batteries often have a lifespan of around 5 years, so while replacing that feels early, it's pretty typical.

 

Different vehicle but my 2019 F250 6.2 began going into deep sleep mode within about two years. It always started fine from deep sleep mode. When I drive my truck, usually the shortest drive is thirty-five minutes minimum each way. I took that deep sleep mode as an indication the battery was weak and replaced the battery with an Odyssey Extreme. Almost five years later with the same battery and it never went to deep sleep mode yet.

 

As others have said, it really is likely that the battery is getting weak. Not 'dead,' and it might last a few more months, but getting weak. It's worth it to either put it on a maintainer or at least a charger for a couple hours at a low setting, to see what happens.

The days of a battery lasting 7+ years are all but gone. With all the electronics on newer vehicles (especially since probably 2017/18), every module has what is known as KAM, or Keep Alive Memory, which helps them maintain settings. Every instance of this KAM draws from the battery, and there could be 5 or 6 or more modules with KAM in them. So the drain on batteries in newer vehicles is kinda extreme, compared to the old days.

Many people today are lucky to get 4 years out of a battery at best, sounds like your son has done well to get almost 5.

Word of warning, don't let the battery get too weak, or you'll start to get all kinds of weird issues. I'm active over on Bronco6g (I recommend heading over there, actually), and usually when someone's battery starts to get weak, they'll start getting all kinds of errors and warning messages that clear right up with either a full charge or a new battery.

And yes, once you put a new battery in, letting it sit for 8 hours seems to do the trick of resetting the BMS. There's a way to force it to do it faster but I don't recall how.

 

Tried putting it on a charger overnight - 2 amp, no change. He's got an appointment at the dealer for some routine maintenance and will have them check it out.