So I've been having this problem since last winter when it started not working. I finally put some attention to it by researching sites and changing some stuff.

So I changed the fluid to the blue type II stuff. What came out was red, but wasn't stinky and was full. I never had any grinding or locked into 4x4 mode problems.

I changed the encoder motor and put a refurbed TCCM in. I did a bit of testing on gravel today and it spun out and fish tailed. No hint the AWD was active. Also I have checked both fuses that I'm aware control the AWD. One in the cab fuse panel and one under the hood.

I have no light on the dash. It doesn't even come on when the key is turned to the on. I know the LED is NOT burned out because just last week before I did this work it was coming on now and then. Now that was weird, but when I went to change the computer out I found a bit of moisture. So some rain must have got down there and maybe was doing something, I don't know. I was messing around with the computer prior to this and didn't see any water.

If the speed sensors were bad, the dash light should come on, right? I'm at a loss on this. It ticks me off they have to keep making things more and more complicated. Any input on what to check would be cool.

 

Have you done a visual check of the 4wd actuator to see if there's any cracking of the rubber boot or the vacuum tubing running to it?

 

The AWD trucks have a front axle that is always engaged so no 4wd actuator, cable, etc. to go bad. They are quite sensitive to the quality of the fluid used as the viscous coupling (same as the NV236 Auto4wd trucks uses) requires specific fluid to stay healthy.

The newer NV136 can be somewhat challenging to diagnose. The last time I was working through one, I needed to use my bi-directional scan tool to monitor both of the speed sensors as well as the AWD commands between the TCCM & encoder motor. In this case, we diagnosed it to be a faulty encoder motor so further testing into the functionality of the hard parts wasn't necessary.

Your case sounds like you may have a failed viscous coupling inside the transfer case. You can test this by lifting one front wheel off the ground with the encoder motor removed. Then, with the appropriate sized wrench, actuate the shift sector shaft while an assistant rotates the front tire. As the shift sector shaft is rotated, it should start to lockup the front output which should result in it getting more difficult to rotate the front wheel. If it never gets all that hard to rotate the front wheel, then there is something wrong inside the transfer case. If it does, then things inside are working and you likely have an electrical issue somewhere in the system.

If you have verified the mechanical system and are back to the electrical, I would start with verifying all of the power/ground wires at the TCCM & encoder motor. Poor circuit continuity can result in the encoder motor not having enough torque to properly apply the viscous coupling which sends power to the front driveshaft. A bi-directional scan tool can command the TCCM to lockup the transfer case at which point you could attempt to spin one of the front tires by hand and see if you get the same resistance as previously found in the manual actuation test done above, this time with the encoder motor applying the viscous coupling.

 

That all makes sense. It's finding a deep scan tool that is the real problem.
These vehicles aren't worth very much money at all, so sinking a bunch into finding and diagnosing or fixing things like a whole transfercase wouldn't make much sense.

I would like to find a schematic or walk through on testing the inputs/outputs of the cables leading to the computer.

I don't know, it's pretty disappointing.

Also, wouldn't the computer have some fault code if it commanded AWD and the sensors showed nothing happening?

 

Did u ever figure this out