http://thenissanpath.com/viewtopic.php?t=9679
In the absence of a scan tool like the Consult II the Factory Service Manual has a list of testing procedures and expected voltages at the respective pins at the TCU and 4wd selector switch. The TCU is in the lower left corner of the drivers dash area. You need to pull back the lower door area trim to access a screw then remove one additional screw on the right side towards the center console of the lower drivers panel, then the panel is snap fit at the top so just pull it out.
Part of the diagnostics will have you rotate the 4wd selector switch with some combination of key turns or brake/accelerator pedal pushes. I don't remember exactly now because for my issue those procedures did not apply. My 4wd selector switch was being blown because of a power back-feed from the TCU. This will net you a series of flashes to troubleshoot with the table in the manual.
If you get nothing from turning the switch it may be toast. You won't know this until you pull the switch though. The power used to light the switch runs on a different circuit than the power used to cycle the actuators.
I had no lcd display (it had power) but no 4wd light at first. Eventually the 4wd light did come on.