Check 4x4, tire chains

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mathman

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My 2021 gen3 (12k miles) won’t reliably go into any drive mode except 2H. This happened a few weeks ago, dealer can see me next week, should be an easy warranty fix, right? Only problem is that I live in the Sierras at 7800’, and it’s been dumping snow since the problem started, and there is no end in sight. We just had a couple day break in the storms, and I thought screw it, I’ll just use the ford roadside assistance and have it towed down to the dealer (I unfortunately already have experience with that service). They were unable to find a tow truck willing to come to my neighborhood (pic attached: that’s after a three day break in the storms, just as it’s starting to snow again from the next).

The truck does fine on these roads with ko2s and 4a. In 2h, no way. I tried once last year just to see, would have gotten stuck in every uphil section. Can’t move even an inch in my own driveway, even if I lock the rear diff.

In the old days, aside from waiting until spring, I’d have a good solution for this — wait for a relatively clear day, chain up and drive the 3/4 a mile before I get to a major highway with clear tarmack. But we’re not supposed to put chains on this truck, anybody know why? The rear wheels seem like they’d have clearance even for old fashioned monsters? I actually have a pair of chains that will fit, but only because I’m sometimes in California and they require you to carry chains, even if you’re never supposed to use them.

It didn’t occur to me that not being able to engage 4wd was a likely failure mode, now that I know it is I feel like I need some backup: some winters I’m out in chain control conditions multiple times a week. If chains are really a no go, is there a way to manually put it into 4h, on the side of the road in terrible conditions?

BTW, I’m not sure exactly what the problem is, because since it first popped up I’ve only driven it a few feet in my own driveway while removing snow. When the problem is active, moving from 2h to 4h or 4a will generate a “check 4x4” and then a “service vehicle soon” message (don’t remember exact wording), and the indicator will stay in 2h, and the orange wrench will light up. Going to 4l will give the same sequence, but indicator moves to 4l. However, even with the indicator in 4l, the front wheels aren’t engaged. Rear diff locks fine (and it really locks — I can spin both wheels!). After I’ve tried to go to 4h, if I hit 2h (even though it’s already lit) it displays the standard changing mode messages, and the orange wrench will go out.

When it’s in a bad mode, no amount of trying to change modes, or turning the truck off for a while will get it to engage. But if I let the truck sit for a few days … all modes will work, no problem. But a few days later, problem back. If I shut it down in 4a, next time I start it might give the “check 4x4” message and be in 2h again. I’m pretty sure I can drive it out of here when it’s in a good state, but right now I don’t trust that it won’t pop out of 4wd when I’m in a valley with a 15% grade on each side. Of course, if I’m blocking plows maybe NDOT will tow me out :)
 

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So-Cal-Al-52

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A while back there was thread about using 4L and 4H regularly or you could loose it. Maybe it seized up? if and when you get it figured out I would recommend using 4L on the regular to keep it working. It is also entirely possible you have a separate issue. Please let us know what you find out.

How long since you used anything besides 2H? It is odd that it re sets after sitting, maybe an electrical issue?
 
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mathman

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The problem showed up New Years Eve after I driven a couple hundred freeway miles in 2H (and driving rain). Before that it had been in 4a for about six weeks. Once it starts snowing I’ve been putting it in 4a and leaving there unless I’m on dry tarmack for an extended drive.

I had it in the dirt in October (sporadically maintained county roads, but dirt). Mostly I was just bombing down them in 2h, but I did put it into both 4h and 4l for short stretches. And while in my driveway the last few weeks, it gas gone into both 4h and 4l — and really went in.
 
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mathman

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Just got the truck back today. The problem was the left front IWE. Dealership just replaced it, but said a problem there is consistent with the intermittent trouble I was having. Seems like it was an easy fix, but there was a couple of week delay while they tracked down the part they needed to replace. Everything seems back to normal, and I can get up my driveway again ;)
 

downforce137

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so the issue with chains has always been clearance in front.. the upper control arm is pretty close to the tire with stock wheels. if you added a spacer or wheels with more backspace, chains can probably be used... maybe..
 
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