KUSA

My 4WD is not engaging. If I had a schematic I think I could figure this out but Haynes didn't see fit to include it in their manual. I can't seem to find a schematic of this system anywhere.
Here is what is going on. The light will not come on in the dash when 4H or 4L is selected. The fron wheels do not pull either. I am not getting any power to the transfer case motor or the clutch. I checked the connector to them but I'm not getting any voltage there either. I checked all the fuses and they are all good.
While I am checking this the switch is in 4H. I am assuming the switch is good but it is not simply a switch as it has a circuit board on it. It has 4 wires. 2 of them have voltage on them. The light green with red stripe has 9.8 volts all the time. The blue wire next to it has 9.8 in 2WD, 7.1 in 4H, and 4.6 in 4H.
It is my understanding that the switch signals the PCM and it powers the transfer case motor and clutch.
Please help.

VTX1800N1

Most likely your IWE control solenoid needs to be replaced. Read: https://www.f150forum.com/f72/how-di...m-esof-186872/

KUSA

Thanks for answering but its not the IWE solenoid. It works fine and even if it was faulty it doesn't have anything to do with powering the transfer case shift motor.

VTX1800N1

Actually, it does, but OK.....

KUSA

How? It's a vacuum system that that disengages the IWEs.

VTX1800N1

It's an integrated system that is vacuum operated but electronically controlled. If the solenoid gets water logged, as they are known to do, you will get no dash light and no 4x4 operation. Ford even has a TSB out about this.

In addition, your measurements at the TCM harness may be faulty. Both the shift motor and the electromagnetic clutch are only momentarily energized until the internal mechanical lockup engages. If you are flipping the switch and then crawling under the truck to measure, it's likely those circuits have been properly de-energized already. If you follow the steps in the thread I linked, you will be able to identify the source of the problem.

Do the 4x4 lights come on momentarily when you start the truck?

KUSA

The lights don't come on at all. I'll follow the link and see if I can come up with something. You don't know if anyone has a schematic on this do you?

VTX1800N1

If you get no lights during the lamp self test at key on, you likely have a 4x4 control module defect.
Sorry, I don't know where to access a schematic.

KUSA

Actually the lights do come on for a moment when the key is first turned on.
I changed the IWE solenoid out for the heck of it to the new style with the rain cover. It didn't make any change. I guess I need to see if the shift motor gets power briefly. I'll get someone to put it in 4H when I'm under the truck with the meter hooked up.
Thanks for following along and giving guidance.

VTX1800N1

Upgrading the solenoid was a good thing. If it wasn't a problem now, it would be in the future. The rain hood is a redesign from Ford to prevent problems. Next, follow the thread I originally linked to so that you can isolate the problem.