i found another post where the guy had the same issues. he says he replaced a hall sensor PT# 1L2Z-7F293-BA and fixed the issue. i took mine out and cleaned it with no change.

 

Where would this sensor be located at?

 

Get under your truck and locate your motor shift t-case, you should look to a few inches below where is the speed sensor is a plastic plate with three wires, green, black and gray, this is one of the hall effect sensors , this is for the rear differential, behind the t-case shift motor, must be located on Hall Effect sensor for the front differential.

 

you should check out the T-case electric clutch relay block, is behind the instrument panel, passenger side, below the oval.

 

i wonder if this could be related to the issue i had a few times last winter when i was in 4x4 high it would start clicking behind the dash and the lights would switch between A4wd and 4x4 high but it stayed engaged in 4x4 high. could it be related?

 

The transfer case relay is above and behind the middle center vent closest to the driver. It is the rear square box, you can pick one up at a junk yard. My four wheel drive would not engage when moving the switch but it would automatically engage just fine. The replaced with a fit in my pocket relay from the junkyard. The old relay switch would cause the relay to cycle when i would put the truck into neutral at a stoplight. I did not read the whole 4 pages of the post but i am very familar with the 4awd system because someone wired in the defrost switch as a master switch for my 4wd system caused a lot of other issues for me. The speed sensor is located in the rear diff cheap part not usually one to go bad. The other sensor to worry about are the hall sensor in the transfer case and the torque on demand sensor in the transfer case. If the truck engages when you put it in 4HI the speed sensors are find it will not engage it is they are off. Is your speedometer on that is the other question that will rule out the speed sensor. The switch transfer case relay, hall effect sensor and torque on demand sensor which is what make the automatic work is what you are in need of looking at. If you need any wiring diagrams i have the massive electrical book for the truck, and will be able to post scanned images i or post them with a link to them. Hope this sheds light on the overall workings of your 4awd. I dislike it and am trying to get right of my truck after i blew up my differential. Sucks because it is a one of a kind no other has been built like it.

 

alrighty so i got under the truck again today.

so it looks like there(they look idensitcal) are 2 hall sensors in the t-case, the rear one is easy to remove and replace but the front one is blocked by the shift motor. i'll update once i get the sensors and take a day to mess with it. i really want to get the A4WD working again.