Yeah i am having the same problem with mine. Where was the sensor located? The Truck has a QD32 motor
I have done the test indicated in the http://www.navara.asia/showthread.php?t=4674 thread and all the gauges moved which seems to me like it will be a sender problem for the tacho.
yeh mate the sensor is on the timing case just beside the water pump on the alternator side. I traced the wires back to a plug probably 200mm away from the actual sensor itself and found the snapped wire at that connection
ok seems like i found the problem. after i cleaned it with rp7 it worked for a bit then went dodgy again so i bought some electrical cleaner and tryed that. works fine so far. see how we go. Thanks again