Are you sure the diff sensor itself is failing or are you doing a temp. repair by plugging/unplugging the connector to the sensor and moving the nearby wires around?
There are lots of reports of the leads to the diff sensor rubbing on the E-brake cable or the chassis somewhere.
You did a good thing to drain and refill the rear diff and replace the sensor but did you clean out the diff before re-filling and re-fill with the correct oil?
Reason I ask this is that all 2005 KJs have a TSB issued...I will try to find it sometime..whereby the rear diff was fitted with "incorrect" oil which caused the diff sensor to fail.
The fix for this was for 2005 KJ owners to take their KJs to a Dealer whereupon the diff oil would be drained...diff cleaned out completely and re-filled with "correct" oil and new diff sensor fitted.
I do not know what diff oil the Dealers fitted to fix the problem or what diff oil originally caused the sensor to fail