Stuck in 4 hi , changed the buttons on dash, changed transfer case shift motor lights on 2 hi flash but then it goes back to 4 hi any help ?

More then likely the problem is in the motor of the transfer case controller

If the switch was in the 2WD position and the transfer case was locked in a 4WD range, my 2 SWAGs would be bad switch or the connector to the shift motor is damaged / corroded or the fuse to the transfer case shift relay module is blown ( fuse # 17 ) / problem with the transfer case shift relay module.

This is without knowing if the truck was used in 4WD the night prior, and shifted out just before turning off. If this is the case, the shift motor might be stuck, and a few hits with a dead blow hammer to the transfer case might jar it free again ( do not use a metal hammer, it could damage the transfer case ).

The vacuum shift solenoids on the firewall are controlled by the GEM ( Generic Electronic Module ) which is grounding either the 2WD or 4WD solenoid, depending on the shift plate contacts in the transfer case. ( when in 4 or 4H, the contact switch plate signals the GEM, which in turn grounds the correct solenoid ).

Pulling the switch will not cause the transfer case to go back to a default position, the switch has a resistance level for each mode, and needs that value to operate the shift motor.

The resistance values for the switch between the 2 dark blue wires:
2WD - 4100 to 3700 ohms
4H - 1050 to 1150 ohms
4L - 380 to 340 ohms
- find the wire locations on the switch, mark them and remove the connector to test the resistance.

Just my opinion on the order :

1. Check the fuses for the shift motor
2. Try the old school shift method, back up ~ 50' put into park or neutral, and shift from 4WD to 2WD.
2.1. This is to see if the transfer case shift motor is bound up, and reversing might release it
3. Try hammering the transfer case with a dead blow hammer while someone shifts from 2WD to 4WD. You only need the key in the run position, if it happens quick enough after running the engine, the vacuum reservoir will still have enough vac to operate the solenoids. Don't chance running yourself over.
3.1. If this frees up the shift motor and the vacuum has bled off, you can try starting the truck and shifting into 4H then back to 2WD to get the front axle to disconnect or manually vacuum operate the front disconnect motor by applying vacuum to the pink vacuum line on the shift motor on the front axle.

First, you do not need 4 low unless you're stuck out in the bush somewhere. Secondly, when you shift from 2 high to 4 high, it goes in immediately. To access 4 low, the tranny shifter must first be put into neutral, wait five seconds, then shift into 4 low. To shift out of 4 low back to 4 high, you must shift into neutral for 5 seconds again. They both flash at the same time because you have not shifted into neutral gear with the transmission.

Did you ever think of having it diagnosed by a qualified repair shop ? Thier are aspects associated with this system you have no clue about. That's the first thing every one goes for , changing the switch . It flashes because codes are stored .
DTC B0768 Service Indicator Circuit High
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 C0357 Park Switch Circuit High
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
You need a professional scan tool to check for these codes an too view data parameters .
Transfer Case Shift Control Module
The transfer case shift control module uses the VIN information for calculations that are required for the different calibrations used based on axle ratio, transmission, tire size, and engine. The system does not know which calibration to use without this information.
The direct battery supply line (CKT 1640) provides the power to the module and motor circuitry.
Transfer Case Encoder Motor
The transfer case encoder motor consists of a permanent magnet (PM) DC motor and gear reduction assembly. It is located on the left hand side (drivers side) of the transfer case. When activated it turns the sector shaft of the transfer case (clockwise or counter clockwise) to shift the transfer case. The encoder motor is controlled with a pulse width modulated (PWM) circuit within the transfer case shift control module. This circuit consists of a driver on both the Motor A and Motor B circuits. The encoder motor is bi-directional to allow the motor to shift the transfer case from 2HI or 4HI to neutral and 4LO positions.
Transfer Case Encoder
Your best bet ,take it to a qualified repair shop .

Your transfer case encoder motor [the thing that shifts the transfer case] is located on the LH side of the transfer case. I believe the control module should be located behind the dash near the light switch area.
If it stays in 4-Lo and the push button indicator just flashes for a while when you select, say, 2 Hi then stops blinking and goes back to the 4-Lo position then I would have someone hook up and check to see what service codes are present. I see a lot of encoder position sensors go bad but you really need a scan tool hooked up to the system to be able to watch what is happening as the shift is attempted. There aren't any vacuum controls on this system.
Hope this helps you out a bit!

there is a neutral switch tied into the transmission, the transfer case will not shift into 4 hi unless the trans is in neutral or park, and 4low only if the trans is in Neutral and the transfer case is in 4hi. CHECK- transmission neutral switch, transfercase feedback switches.

sounds like the shift motor on the transfer case is going bad.

i have a 1993 blazer 4.3 w code 4x4 with a 4L60 E . my truck wouldn;t go in 4 hi or low. so i changed the transfer case motor and it works fine now. If you turn the ignition key to on but not crank the engine and open the driver door and push 4 hi button, you should hear the transfer case motor cycle for 3 or 4 seconds every time you push button and the light will flash until it goes in 4wd If the 4 hi button light doesn't flash during cycle then it could be a bad switch. if the transfer case motor won't cycle it could be a fuse or a bad transfer case motor . Hope this answers your question.
pgale89

If the light is continuing to flash the 4X4 is not engaged, most likely the motor that engages it on the transfer case is either stuck or defective.

are any of the lites on the switch flashing? you may have a sticking 4x4 shift motor on the transfer case. with a helper, key on someone under vehicle at shift motor, one operating the 2wd button, give shift motor a rap with small hammer on metal portion of shift motor to see if you hear it trying to work. to access control module, remove plastic right kick panel and its right there. remove connector and inspect for corrosion or bad connection. also try park and neutral, may even have to be rolling a bit to disengage. let me know how you make out and will help further if i can. do you know what transfer case system you have? np1 or np4?