Try jacking up the rear of the vehicle and place jack stands under it so both rear wheels are off the ground(chock front wheels first) engine off, ignition switched to on, transmissino in neutral, select low range and make sure it engages and the centre diff lock light comes on and does not flash, have some on operate the rear diff lock switch while you are down the rear end listening for the rear diff lock motor to start, if you hear a noise then grab hold of one rear wheel and rotote it back and forth and see if you can get the diff lock to actuate and lock up. If it is locked you will not be able to turn the wheel. If this is the case and your rear diff lock light is still flashing, then the most likely cause is the diff lock detection switch is sticky (but other things are possible). If you hear no electrical motor noise from the rear diff and can't get it to lock, it could be a number of things, fuses, rubbed or burnt wiring, rear diff lock control ECU, diff lock motor and switches in the diff etc etc. Do a search on this forum for info about the burnt wiring near exhaust, which has been mentioned before. If you don't have the wiring diagram for it PM me.