15 F-150 engages 4WD randomly
 

Original owner 15 F150 Screw xlt 4x4 3.5 EB 32K miles. Mostly highway towing 3K # trailer.
Two weeks ago I used 4wd in yard and when I shifted to 2wd it said it did but really did not.I tried backing up, spinning tires all that. After a mile of pavement it came out on it's own.
After parking and then driving home, it had switched itself to 4wd for real but not by the switch or indicator light. Eventually it switched itself back to 2wd.
It very obvious when it's 4wd by jumping and tires slipping when turning even though the dash says it's 2wd.

Two days at dealer, they finally replaced the motor on transfer case and it works fine now.
I drive it for one day then the same problems return. When you start the truck, even if it was 2wd when parked, it will be 4wd and stay that way for miles.

On day 3 at dealer this time. They and Ford tech assistance seem to have no idea.

I though replacing the motor was BS when they did it, even if it was bad how did the hubs get engaged if the solenoid for them it being told 2wd? Both the transfer case and the hubs have to be engaged for 4wd.

I will update when I get info. Has anybody else had this issue, I couldn't find any.

When the truck is shutdown, the IWEs fail to the engage position. During cooler, about 32F and below, they will stay engaged for about 2 miles to warm up the front diff. It will do that every key cycle while the ambient temp is down in that range or lower. The Tcase shouldn't be in 4X4 though. There is another member here who has a bad Transfer Case Control Module, TCCM, not saying that is the trouble, but a place to look.

Wow, thanks that explains a lot. The problem always reappeared when it was cold outside and the key cycled, even it the truck was warm.
The temps here this week have been from 6F to 55F.
I imagine on the warm days the hubs were not engaged but the transfer case was and I didn't know since the tires didn't slip and jerk.

You're very welcome. I'm not sure if it mentions anything like that in the Owners Manual, TBH, I've pretty much read hit/miss in it.
Here is something you can try, and totally no guarantee it will fix anything, but try a KeepAliveMemory, KAM reset. All you need to do is disconnect your negative battery cable, turn your lights on to draw whatever power there might be, and let it sit for 15 minutes, then reconnect. Your radio settings, clock, and maybe a few other settings may need to be reset, but if it solves your Tcase engagement troubles, it'll be worth it. Sometimes resetting the KAM, cures a variety of problems.
Forgot to mention, when you do that, your trans will shift funny until the TCM relearns your driving style, throttle response and shift points will be different, but should clear up in about 100 miles or so.

It's still at the dealer. I know they didn't do that before since none of my settings were lost. The powertrain warranty paid for their first attempt to fix this but I have the Premium extended for $100 copay if not so I'm not worried about the cost just want it fixed.

Understand. They may have done a reset, but they do it a different way. I think they use IDS, resets the modules, but doesn't screw with radio etc. They did that on mine the last time it was in to help out with the engine/trans surge, along with the TSB.
I also had a tuner I could that with, and did a few times. Not sure if my current tuner can do a KAM reset.

They still have no idea, today they replaced the solenoid for the hubs and nothing changed. I am really disappointed that Ford corp is not giving them better info. I asked when they ordered the solenoid how a hub solenoid was going to affect the transfer case being in 4wd and got a run around answer. They did ask if I wanted a loaner but I said only if it's a truck so I can do truck stuff ( they didn't), I have a 18 Fusion sport I'd rather drive than a low end loaner car.

Still not fixed, I know they tried a new transfer case control module and it didn't fix it.
So far that I know of:
Transfer case motor, IWE solenoid, control module.
I showed up Saturday morning to see if my truck was even in the shop or sitting outside with a foot of snow on it. It was inside, I told them I'm ready for the loaner now, suppose to get it today. They said it would be a Flex so that's better than I expected but I still need a truck.

That isn't good news at all. The TCCM controls the solenoid, but you wouldn't expect to go to 4H/4A unless it's called for by you. It is possible they may have got a bad module right off the shelf.
What ever the outcome is, please post it. You don't seem to be the kind that's afraid to ask questions, so please do.;)

I swear the other day I was driving out of St. Louis when it was real cold and thought my truck was in 4wd even though the knob was on 2wd. It was very cold out so I thought maybe it was supposed to do that. Eventually as I got more South and the temp started raising, it didn't feel engaged any longer. Has felt fine every since but I'm back in MS now.