Disco1 - no. Again - matters not if you engage cdl or not - its not controlling power distribution between wheels on same axle. It controls power distribution between axles. Aka - if you cant move BOTH wheels on one axle, then you shouldnt be able to move BOTH wheels on other one. Basicall to check if cdl is not or not with your method you need to jack both wheels on same axle up, and then try to rotate them at same time. They shouldnt spin
However if you raise just one - it may spin, even though cdl is engaged. Thats why people buying all those lockers and limited slip diffs.
ColeCam - yes, thats the one that you should see. If its not lit up there are usually few reasons to cause this:
- electrical glitches (even though its mechanical - go figure)
- leveler is broken (not likely, imho)
- lamp is burn out
- you trying to engage cdl when transmission "wound up" - same thing will cause issues with disengaging lock. You basically have to let track to go up/down one gear to get engaging working. Or you have to be standing still. And yes - manual doesnt say so - but its general condition on which locking/unlocking is easier. So if you trying to engage things while driving in 1st gear with RPMs around 3K - it may refuse to do so.
In order to check if things are really really engaged - raise up front of truck on 2 jack stands.
Stick jack under diff housing and raise rear. Or if you lucky to have 4 jack stands - do same raising with 2 stands for rear.
Now crank truck up. Put it in first gear. Go to rear or front and either together with friend or using some long stick try to block both wheels movement at same time (wheels on same axle). Notice how other axle keep spinning.
Now engage CDL. Matters not if light isnt coming up.
Try to do same blocking. You should have utterly hard time to block movement. And when you finally do - other axle will stop rotating.
If it happens - you got cdl working, its just light that wont.