.....my 5 cents.... about JDM
May be take a look in rodeo or troopers manuals for 2wd-4Hauto-4Lo schematics. trooper (2001) utilizes vac control solenoids to move lock ring in front axle to connect/disengage driver side front shaft. on one of the troopers I have in the shop the TOD check light was flashing till I fix one of the vac control solenoids.(was not going to 4wd mode).