4WD hi light not coming on and no 4WD engagement.
I have a 2004 f-150 lariat with 160k miles. 5.4l
Here is what I have tried after reading this forum.
I checked all the fuses and replaced them to be sure. #'s 11(10 A), #20 (15 A), and # 29 (15 A). still nothing.
I then taped the transfer case motor as suggested with no result.
I then replaced the transfer case motor and still nothing.
I also replaced the IWE solenoid.

Any suggestions would be greatly appreciated.
Thanks,
I just joined, but have visited before for other problems

 

All good.
It was a bad 4x4 relay in the auxiliary relay box in the engine compartment LH fender.
R01 and R02 .
I only wish I had tried this first. Cost only $9.99 at advanced auto parts.

Thanks,
Hope this helps someone.

 

Congrats on figuring it out! I moved your thread into the appropriate section so that it CAN be of help to others. Glad to have you with us!

- Jack

 

I'm having the same issue with the same truck you have. How did you figure out it was R01 & R02? The owners manual does not list either of those as being 4x4 relays. Already checked the other fuses. What does taping the transfer case motor do?

 

The relays are listed in my owners manual. Try swapping the relays to see if it works. They are the same relays. I was able to diagnose after swapping the relays, It then went into 4 x 4 and would not go back into 2 WD.
Tapping the transfer case motor can help if there is a dead spot on the motor.

.

 

I switched around R01 & R02, to no avail. I tapped on the transfer case motor and did get it to finally engage, so the problem is definitely the motor. I have a new one on order.