I have a 2005 Off road and I just put in some 4.88 gears with an ARB locker up front. Well I took it for a test drive right after we finished putting the gears in and when I shift into 4-Lo my TRAC and ABS systems are still engaged in 4-Lo and I'm pretty sure they should be disengaged when in 4-Lo.
I just checked everything over again (wiring and all) and when I shift into 4-Hi and 4-Lo, only the VCS light comes on. With the locker engaged the ABS and "vehicle swerving" lights are added.
When I took it for a test drive both the TRAC and ABS systems are working in 4-Lo, but are disengaged with the locker on. I found a steep rocky hill and tried to creep up it in 4-Lo. All that happened was the tires started to slip and TRAC engaged and I went no where. I engaged the rear locker and was able to spin the tires all I wanted on the hill. Coming down it I pretty much flew down it in 4-Lo (diff unlocked) because the ABS system was trying to not let the wheels slip which was impossible on that surface.