2002 dodge durango 4.7 4x4 4DR - The four wheel drive system is not working. Can't shift from 2wd to 4hi, no sounds or movement from transfer case motor and no lights displayed on the electronic shift to indicate the drivetrain. Removed dash cleaned switch harness and reinstalled.

The reason the light is flashing constantly is because the vehicle is sensing that four wheel drive(4WD) is not working. These 4WD systems use vacuum from the engine to engage/disengage to front axle. The vehicle probably has no vacuum going to the front axle, which would not allow the 4WD shift to complete, which would then leave the light on the dash flashing.
First thing to check is that the vacuum actuator on the firewall is working as it should.

It might sound funny but sometimes you have to back up to get them out of four wheel drive mode...worth a try...Hope this helps....GOD BLESS....Randy

On the transfer case
Transfer Case - Electronic Shift
The four-wheel drive electronic shift-on-the-fly feature electrically shifts the vehicle transfer case between 2WD, 4WD HIGH, and 4WD LOW. The system mode is selected by the operator through the mode select switch (MSS) on the instrument panel. The operator is informed which mode the system is in by two instrument cluster indicators: one for 4WD HIGH which appears as 4WD, and one for 4WD LOW, which appears as 4WD LOW. Shifts into 4WD HIGH can be made at any speed. When shifting into 4WD HIGH with the vehicle stationary, tooth blockage may occur preventing shift completion. When the vehicle is driven above 8 km/h (5 mph) the shift will complete. When shifting in or out of 4WD LOW, the four-wheel drive (4WD) control module requires that the vehicle speed be less than 5 km/h (3 mph), the brake pedal be applied, and the transmission be in NEUTRAL (automatic transmission) or the clutch pedal be depressed (manual transmission).
The gearmotor encoder assembly is mounted externally on the transfer case. It drives a rotary cam which moves the mode fork and range fork within the transfer case between the 4WD HIGH, 4WD LOW, and 2WD range positions.
The four-wheel drive (4WD) control module controls the gearmotor encoder assembly that shifts between 4WD HIGH, 4WD LOW, and 2WD modes.

Which do you have ?
Transfer Case - NVG 236 (Two Speed Automatic)
Transfer Case - NVG 233-NP1 (Two Speed Selectable)
The NV236 transfer case is an automatic transfer case with three drive ranges. Shifting from rear wheel drive to four wheel drive is done automatically when the transfer case shift control module receives wheel rotating slip information from the speed sensors. The transfer case shift control module then engages the transfer case motor/encoder to position the transfer case from rear to four wheel drive. When the transfer case shift control module receives information that the wheel rotation is the same on both axles, the transfer case shift control module sends position information to the motor/encoder to put the transfer case back into rear wheel drive. The three drive ranges are 2HI, 4HI, and 4LO. The 2HI position is for normal driving with the rear wheels pushing the vehicle. The 4HI, position is for driving through sand, snow, mud, gravel, or heavy rain at normal or slightly below normal speeds. The 4HI engages the front axle to allow for four wheel drive. The front axle is pulling the vehicle, and the rear axle is pushing the vehicle. The 4LO range is used for off road driving, heavy snow, deep mud, or shallow fording. The 4LO is similar to the 4HI except that the gearing in the transfer case is set for low speed and high torque. The NV236 is manufactured at Syracuse New York by New Venture Gear a division of New Process Gear for General Motors.
Is the switch light on or flashing ? If you have automatic 4x4 there are several DTC'S that can set >
DTC B2725 ATC Mode Switch Circuit Malfunction DTC C0300 Rear Speed Sensor Malfunction DTC C0305 Front Speed Sensor Malfunction DTC C0308 Motor A/B Circuit Low DTC C0309 Motor A/B Circuit High DTC C0310 Motor A/B Circuit Open DTC C0315 Motor Ground Circuit Open DTC C0323 T-Case Lock Circuit Low DTC C0324 T-Case Lock Circuit High DTC C0327 Encoder Circuit Malfunction DTC C0362 4LO Discrete Output Circuit High DTC C0367 Front Axle Control Circuit High DTC C0374 General System Malfunction DTC C0376 Front/Rear Shaft Speed Mismatch DTC C0387 Unable to Perform Shift DTC C0550 ECU Malfunction DTC C0611 VIN Information Error

sounds like the transfer case may have crapped out on you and possibly the transmission

2wd to 4hi to 2wd can be done moving or stopped .. if moving shifts can be made up to 55 mph with the vehicle in motion, the transfer case will engage/disengage faster if you let off the gas pedal after turnin the control knob. if the vehicle is stopped.. the key MUST be in the ON position with it running or OFF the shift cannot be done if the key is in the accessory position

4x4 issue could be either the TCCM Transfer Case Control Module, or the transfer case shift motor.

When you turn your dash switch from 2wd to 4HI, can you hear the shift motor underneath operating?

there are 2 systems.
one is a part time system only.the 4x4 locks and is for ice mud and snow.Driving full time will damage the transfer case.The other system is a full time system and the selector says 2wd,4wd part time ,4wd full time and 4 lo. if in full time,it can be driven all the time even on dry roads.The full time is really an all wheel drive system.
the 4low is a very low gear and the main shifter has to be put in neutral and then the transfer case put in 4 low.attempting to put it in 4 low while in "drive" will make a gear grinding noise.
getting out of 4 low is the opposite.shifter to neutral and then put it in 2wd and then in drive.The newer durango has an electronic transfer case with a dial on the dash.The 2002 was available with 2wd,4wd,awd and 4 lo on a switch.The 1999 has the lever on the floor .

try resetting the 4X4 module first. Remove the courtesy lamp and ATC fuses for at least 1 minute the reinstall fuses. Cycle key on and off 5 times then try your four wheel. Please rate if this works.

you will need to let the durango sit in the nuetral position without moving, then turn the knob from 2WD to 4WD. if that doesnt work, try putting the durango in reverse and then back to drive a couple times. you may have some mud/dirt/oil caked up under there interfering with the 4WD moving parts.