There are a few things that could cause this. I have read about a few on this forum, from a simple faulty switch or similar, to a problem in the rear end itself. Mine went on because a clip in the rear end broke, so the truck thought the diff was locked all of the time. The dealership replaced my whole rear end. Nissan makes it as an assembly, rather than having replaceable parts. Luckily mine was under warranty.
2007 nismo kc 6m. k&n fipk cold air intake, cxj intake manifold spacer, hypertech max energy programmer, banks monster exhaust 3", jim wolf tech lightweight flywheel, clutch disk, pressure plate, tjm md extended travel coilovers, tjm hd raised leaf packs and extended travel rear shocks, toyo open country at2 265/75r16, kicker 5ch. amp, pioneer 6x9" and 6-1/2" speakers, 12" rockford fosgate p3 sub in a sealed box, aluminum utility cap, auto ventshade ventvisors, weathertech floor liners, coverking seat covers.
still to come; oem nissan cam bolts, sliders, skids, bumpers, lightweight pulley, e-fan.