ADD troubleshooting

Recently my 4wd decided to stop working, leaving me to travel the maze in 2wd. I have read endless threads about the Automatic Differential Disconnect (ADD) being problematic and prone to failure. I am getting a bit confused with the entire electrical process between the shifter switch and the ADD itself. I haven't found any great diagrams of the electric only actuator, just the electric/vacuum type. Perhaps some of you can help me understand and work through the process of elimination.



My truck is a 2004 Tacoma 3.4 liter auto and J-shift transfer case. When I shift into 4wd the dash light does not illuminate. I can hear the 4wd relay clicking with the shifter moving from 2wd to 4wd. With the 4-lo engaged I do get low range but still just 2wd.



If I understand correctly, the shifter pushes a switch which then switches a relay turning on power the ADD motor. The motor drives a gear that slides a sleeve from the passenger axle shaft onto the driver shaft locking the two together. Is that right? What is supposed to make the 4wd light come on and blink? Is it the sensor on the t-case?



I pulled the plug from the ADD and tested the pins for power. There are 6 pins total and pins 2,3 both had 12v while in 2wd. I repeated in 4wd and had 12v at 3 and 11.5v at pin 6. This leads me to believe that the problem is inside the ADD motor and probably has a bad contact inside.



I don't want to order a new motor unless I'm sure that's the problem since they are expensive. I also have to drain duff fluid to pull it out and inspect it so I'd rather not since its my DD. Please help me understand this a bit better so I'm not wasting time and money. Any further insight would be greatly appreciated, thanks

 

Anyone have any input?