I was under my '06 H3 the other day diagnosing a pulling problem while braking. Seized caliper. Font end jacked up and went to turn the front driveshaft. Turned a bit as well as the front free wheel and stopped. Panic ensues! Right away I'm thinking its in 4WD lock! Switched from 4hi to 4hi lock. No change. Out of the garage I go. I'm next to a gravel parking lot so driving in circles between 4hi and 4 hi lock. No transfer case windup. After about 10 minutes of NASCAR roundie round in and out of lock I can't feel a difference. Driving home I suddenly realize the truck was in park when the front end was in the air. (Face palm) dumass! I feel relieved that driving it won't wreck anything. Then it hit hit me. (face palm) dumbass! There was no difference between lock and unlock while doing circles. Something is wrong. Next day up the front end goes. Replace calipers. Transmission in neutral, 4hi and the front driveshaft turns fine. Tried 4hi lock and the front driveshaft spins free. Hmmmm... It shouldn't turn. Lets try 4lo lock. Driveshaft is not able to turn. So here is my dilemma. I am understanding that the lock is in the 4hi to 4hi lock shifter fork and the 4lo shifter fork engages high and low speeds in the transfer case. Meaning that if the lock shifter fork was broken in a non-lock position I would also have 4lo non-lock. Is it possible that my shifter fork is fine, but my encoder motor is messed up. As I'm typing this I realize I did not try 4lo doing the roundie round. (Face palm) dumbass! Any productive help with the transfer case would be appreciative. The dumbass is going to have to work on his own problems.

 

You could simply remove the bolts holding the encoder motor and activate each setting 4normal-4hi-4lo.
If the motor gear doohickey works it will advance. If not theirs your culprit.

 

Of course you'll need to have the cable plugged into power it.

 

If you put any H3 on a lift, disconnect the Transmission cable from underneath placing it in neutral (and lockers off) when you rotate either the front or rear driveshaft, at least one of the tires to that corresponding shaft will move. That is because on a lift, there is no load, nothing is stuck.

On gravel it would be difficult to tell when T Case Lock is engaged.

If you placed it from Hi to Hi Lock front end raised without moving the vehicle, it would likely not go into lock, the T Case needs to be rotating under 5MPH to shift and engage.

Hope something there helps.

 

The Hummer was on a lift. A four post ramp hoist with a jacking beam lifting up the front end. Makes it very nice for checking ball joints and such. Rear tires are not able to turn when on the hoist. I have no lockers. The encoder motor is working fine. This is not my first rodeo with four wheel drive. It's my first with a push button transfer case. I know what transfer case windup feels like, even on a gravel parking lot. Never the less, I'll be rechecking again. I guess the next step would be to engage the hi lock before putting it on the hoist and lifting up the front end. Thank for the info.