Transfer case not working

Check the wiring harness at the actuator for breaks or damage. Also, the check the plug.

Coming to a complete stop and being in neutral would be the norm any time you're going in, or out of 4 lo. Here is the description of a range shift:
Range Shifts
The range shifts are the shifts between the HI and the LO ranges.
"Â 2HI to 4LO

"Â 4HI to 4LO

"Â 4LO to 4HI

"Â 4LO to 2HI

A range shift can only be made with the automatic transmission in neutral or with the manual transmission clutch fully depressed. The shift occurs when the vehicle speed is below three miles per hour.
Whenever a shift into 4LO is initiated, the 4LO shift select button blinks. The 4LO shift select button will continue to blink until the shift is completed mechanically or until 30 seconds elapses. The 4LO shift select button must be on and not blinking prior to shifting the transmission into gear or releasing the clutch pedal.

If a range shift is initiated when the transmission is engaged or the vehicle speed is above 3 mph, the 4LO shift select button will blink for 30 seconds and no range shift actually occurs, the TCCM will default and position the transfer case into 4HI.

Here is the description of a mode shift:
Mode Shifts
The mode shifts are shifts from 2HI to 4HI and 4HI to 2HI. A mode shift can be accomplished in any gear position and at any vehicle speed. If the system is in 2HI, the driver can shift into 4HI merely by pressing the 4HI shift select button. The 4HI button will blink status whenever a 2HI or 4HI shift is initiated and will continue to blink until the TCCM completes the shift. After the shift into 4HI is accomplished, the 4HI status lamp remains lit to indicate that the system is in 4HI.

There is a difference between when the TCCM sends voltage signals in order to engage a four wheel drive shift and when the vehicle is truly in four wheel drive. The transfer case can be shifted into 4HI and the front axle may not be engaged.

The driver can shift from 4HI back to 2HI by pressing the 2HI shift select button. The 2HI shift select button blinks until the shift to 2HI is complete. The 2HI shift select button will remain on once the shift is mechanically complete.

Does this transfer case select switch have an auto 4WD position, or is it just straight selectable.

Next would be to check for codes. On a straight selectable o-auto case, you ground pin 13 at the data connector under the dash. I dont have an illustration of which pin that is, but the wire color is orange. The lights on the switch should flash. You are only going to have a choice of 4 codes. Here is the procedure to further clarify.
Diagnostic Trouble Code (DTC) Displaying
The transfer case shift control module is equipped with the ability to store diagnostic information, which is useful to a technician in the event of module, component or wiring failures. This information can be retrieved from the transfer case shift control module by way of flash codes, which are displayed on the three transfer case shift control switch buttons. These buttons are located on the instrument panel to the right of the steering wheel Before obtaining DTCs, perform the following transfer case control module (TCCM) Self-Test.

TCCM Self-Test
Observe the transfer case shift control switch indicators while turning the ignition switch to RUN. A properly operating system will flash all indicators and then will return to the current gear. If the system is operating normally, then proceed to Displaying Codes.
If the TCCM failed the Self-Test, then test the following circuits.
"Â Battery Positive Voltage (40 and 1640), and Ignition 3 Voltage for battery voltage

"Â Ground Circuit for ground

"Â Diagnostic enable circuit for an open or high resistance

"Â Transfer case shift control switch connector

If the above circuits are normal but the TCCM still fails the Self-Test, replace the TCCM. Refer to Transfer Case Shift Control Module Replacement.
DTC Displaying
Turn OFF the ignition for 10 seconds.
Connect PIN 13 on the data link cable (DLC) to a ground. The DLC is located in the cab under the instrument panel on the driver's side.
Turn ON the ignition, with the engine OFF.
Observe the transfer case shift control switch select buttons for flashing codes. Refer to Diagnostic Trouble Code (DTC) List.
Important: If the transfer case shift control switch buttons all blink only once and then stop, no fault codes are stored in the transfer case shift control module.

"Â When one DTC is stored in memory, that code will blink that number of times followed by a 3 second pause and then repeat.

"Â If more than one code is stored, the first code will blink, followed by a 3 second pause and then the second code will blink.

"Â This sequence will continue until PIN 13 on the DLC is no longer grounded.

"Â If the TCCM will not communicate the presence or absence of DTCs, test the above circuits in Self-Test Step 2. If the circuits are complete, then replace the TCCM. Refer to Transfer Case Shift Control Module Replacement.

The TCCM should be in under the dash. Near the steering column. I don't have any illustrations of it. I can give you wire colors if it will help.

I don't know what they are describing on the transfer case itself, the only component on the case is the encoder motor. The TCCM that I am describing is under the dash near the steering column, that is for selectable FWD. In fact automatic transfer case shift control module is shown in the same place. I did not see any links to pictures.

Check vacuum supply to front axle. If this is an electric shift 4wd, check to make sure the actuator is getting power.

Any noises? If not you must have a broken fork. If yes then check the u-joint.

SYMPTOM TROUBLE SHOOTING FOUR WHEEL DRIVE DOES NOT ENGAGE TRANSFER CASE DIAGNOSIS FOUR WHEEL DRIVE ENGAGES BUT INDICATOR LAMP WILL NOT LIGHT FOUR WHEEL DRIVE ENGAGES BUT INDICATOR LAMP WILL NOT LIGHT 4WD INDICATOR LIGHT WON'T TURN OFF (4WD DISENGAGES PROPERLY) 4WD INDICATOR LIGHT WON'T TURN OFF (4WD DISENGAGES PROPERLY) FOUR WHEEL DRIVE WILL NOT DISENGAGE FOUR WHEEL DRIVE WILL NOT DISENGAGE JUMPS OUT OF FOUR WHEEL DRIVE POSSIBLE CAUSE: CORRECTION: Blown A/C-HTR Fuse. Replace. Faulty transfer sw. Replace. Faulty 4WD Indicator light, sw, or wiring (4WD engaging but indicator light not coming on. Repair as needed. Transfer case linkage improperly adjusted or disconnected. Adjust or repair. Faulty transfer case: Drive chain broken, range selector ring broken Repair Faulty front axle. Repair POSSIBLE CAUSE: CORRECTION: Blown bulb. Replace. A/C-HTR fuse blown. Replace. Faulty front axle sw. Replace. Faulty wiring. Repair open in wiring. POSSIBLE CAUSE: CORRECTION: Faulty front axle sw. Replace. POSSIBLE CAUSE: CORRECTION: Faulty wiring or front axle sw. (4WD disengaging but indicator light staying on). Replace or repair wiring. Transfer case linkage binding or improperly adjusted. Replace or repair. Faulty front axle shift mechanism.