Hi Guys, My 2021 with 38k miles is acting up on me. I use it for work so some days the truck gets started 6-10 times a day. On start up, it cranks over for a second then stops-then fully cranks over and fires up. After driving a few feet i get dash warnings-Hill Start assist warning, Pre Collision Assist not available, Hill Descent control fault warning, no driving modes available(even tow/haul), and sometimes the back interior lights stay on when driving. Once I had the Steering Assist fault pop up and steering was harder then normal. Any ideas what could cause this? THis is going back 3 months of it happening at least once a day.

 

How old are your batteries?

 

^^^ This.

Your battery/batteries are likely getting weak because the truck is 5 years old and sounds like it gets started multiple times a day without getting driven very far. Impressed that they lasted this long. Those error messages are VERY common when the batteries get weak.

 

Batteries are Motorcraft dated 12/25. Only a year hand half old. The same error messages come on even after a start up after 2 hours of driving. I drive it the same way I drove the "same" 2018 and never had these issues.

 

Almost for sure you have a bad battery or two.
Get them LOAD TESTED, and they must be tested separately, so at least one battery needs to be disconnected before testing.
And, if they are dated 12/25 then they are not even a year old yet, so should be under the free replacement warranty coverage.
Believe what we are all telling you, this is a very common issue...unfortunately...

 

I am believing you all! It just blows my mind a $300 battery would go bad like this.

 

My experience with MC batteries are they start leaking very early on.

 

Batteries first, then head to the plug back by the spare tire.

 

Yes, that plug would be next to check, but usually does not affect the starter cranking the engine over.
Now, OP didn't say, but if the issues only come up after it has been very wet, this would be another indicator for this harness plug.
I had hell with mine, but it always started normally, and was only after it had been very wet or icy on the road.

 

OP, so you put a new set of batteries in your 2018 truck in Dec 2025? If so did you replace both at the same time? Also did you do the replacement yourself or did a Ford Dealer replace them? As pointed out you should have some warranty on them if one or both test bad.

I would also check to be sure your alternator is charging correctly. This is pretty simple just use a multimeter on one of the batteries after you have started the truck you should see 13.5v-14.5v. Be sure all 4 of your battery terminals are clean and tight.

One other thing to keep in mind is perhaps you are not running the truck long enough to keep your batteries fully charged. If your starting the truck then only running it ~5-10 min or so then shutting it down you most likely are not running long enough to charge the batteries. You may be able to fully charge both batteries with an external charger so they both are ~12.5v or more then see if they hold that charge. Also if a lot of short trips you may have to leave the truck running 5-10 min rather than immediately shutting down the engine when you arrive at your next spot.

These trucks with all the electronics, sensors, need a very stable voltage for everything to stay in sync. One hint of a lower voltage and the truck goes nuts with errors on the dash. Unlike the older trucks where you could run on unstable batteries for quite awhile as long a it started.

Good luck,

Mike

 

which side how big is this plug...cant just dangle that and not finish, for us newbeees.

 

On the inside of the trailer hitch flange behind the rear bumper.

 

To the OP, if it's not your batteries, check the plug shown in the picture above. All of your electrical gremlins indicate this plug has been compromised on your truck. However I have not heard of this plug causing starting issues. Take the plug apart, clean it out with CRC Electronics cleaner, apply dielectric grease and reassemble. Doesn't take very long and may solve some or all of your issues.