I was going to start with the rear ELSD solenoid, since that one looks easiest to do. I have already purchased solenoids for both the front and rear for a total of $47 shipped for both. I have them sitting in the attic waiting for the next fluid swap interval.
If the rear one does not do it, then I will do the front one. If those do not solve the problem, then I will take it in for diagnosis. I suspect that wiring would be the next issue in line.
'06 XK Limited, 5.7L, QD II, Black, 163K
'02 WJ Overland, 4.7L HO, QD, Inferno Red, 126K