4wd actuator not actuating

unfortunately I’m now realizing I have the least desirable variation. I’d consider myself decent with mechanical bits but this whole electrical thing is really giving me a run for my money

 

You say, the 4WD light came on by itself once?
That can’t really happen. Not without being in 4WD. And not on its own.
The light for the 4WD is gorounded by the 4WD ECM.
It possible it’s the ECM, but it is rare.

like to be sure on the powers and grounds before I’d want to call it that.
Which is why I want to a few more check (above).

 

This was unprompted on the way to work one morning right around when I noticed it stopped working. Popped up after I began driving and went away a minute later. Seems like the only case of this ever.
I have a new ecu on the way from eBay just to check that box but I’ll get back in the truck when I have time this weekend to check the rest of that stuff.

 

Turns out it was the 4wd ecm. It slips right into 4x4 and I confirmed with the front wheels off the ground. Only concerning thing is it doesn’t blink, just no light then solid light when engaged.

 

Nice, did you autopsy the old unit?

The light may not flash if everything shifts right away, it only flashes if it can't complete the shift and/or if there's an error with the limit switches.

 

The sticker on the old computer looks like it may have gotten wet, maybe condensation from the heater. It doesn’t blink at all, when it doesn’t shift right away it’s just blank and then solid light.

 

This seems like a super uncommon scenario and I’m not sure if this thread will help anyone down the road. Anyway, shoutout to @TnShooter @Dm93 @Red_03Taco and anyone else who contributed here, thank you for the help!

 

Pop it open and take a look, it's already busted.

Interesting, like I said earlier in the thread I don't know alot about the 1st gen 4wd system. I've never even seen a 1st gen with the pushbutton system, all the ones I've seen were J-shift.
Seems to operate somewhat differently than the 2nd gen system although the actuators look very similar.

 

I pulled the computer apart awhile back and it looked fine to me, no damage or corrosion. Part of why I was a bit weary of that being the culprit.

 

Ah ok I guess I missed that, we've seen a few of the 2nd gen 4wd ECUs fail for no apparent reason with no apparent damage as well but it's pretty rare.
Had a couple that got killed from lightning.

 

The only wat the 4WD light can come on is through the 4WD ECU.
The light itself has power to it at all times. But the ECU provides Ground to turn it on.
And a lot of criteria has to be met before that light can turn on.

As much as I hate to think it.
It's looking more and more like an ECU issue.

 

It was the ECU, see post #84

 

Glad you figured it out OP. This thread will hopefully help others down the road too. Lots of really good info here

 

Missed that one.
Good he got it figured out.

 

Taking it wheeling this weekend. I’ll report back if anything breaks lol