O3 avalanche z71 transfer case acuator switches from 4 low to 4 high to 2 high by its self

sounds like the transfer case needs rebuilding or replaced check to see if the oil in the case is dark or colored or milkey looking this is a indication the transfer case need to be redone

i would suggest taking to a 4wd repair shop as will need diagnosing with the proper equipment

Yes we can ! With the light on and or flashing , DTC'S - diagnostic trouble codes are stored in the 4X4 control module . Have the codes check , not at auto zone or any other parts stores . There code reader tool will not pull this codes . Need to take to a qualified repair shop . Testing also needs to done , not guessing an throwing parts at it . This 4X4 system can set a number of codes .
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

DTC C0387 Unable to Perform Shift
Circuit Description
The transfer case encoder is a switch that converts a shaft position, representing a mode or range position, into electrical signals for use by the transfer case shift control module. The encoder houses 4 Hall effect sensors that are used for channels P, A, B, and C. These sensors provide a path to ground, when a magnet, (part of the Motor Encoder), passes over them.
The transfer case shift control module supplies an 8 V reference and a ground circuit for the encoder hall effect sensors to function.
The transfer case shift control module supplies current limited 5 V on all the channels, thus as these channels are pulled to ground, the module can interpret the location of the transfer case shift position.
This DTC detects that the transfer case is unable to successfully complete a shift to a requested mode or range.

On those year models with the switch on the dash the switches are bad about going out but the actuator is located at the front passenger side on the transfer case if its a z71 drop.the skid plate on the front and its black about 4 inches long with a short couple of wires coming out the end of it to a plug. Disconnect the battery and then unplug it and take it out a short cressent wrench is best and then just put the new one in but don't over tighten

I don't know what you mean3010 mule is this a chevy . If so look at the acuator cable and the actuator it self and the front carrier switch as well as the shifting mechizium switches for the 4 wheel engage system adjustment and vacuum positvve pressure to the transfer case and transmission

I would check the shifting mechinizuns . If its manual _ cable opperated system have someone shift it see how it moves on the transfer case and how smooth the cable opperation is . The system is bascaly a vacuum opperated system after that but if it goes into 4 wheel then the system is working . The other place you could look is at the front transaxle adjustment _switch witch is a cable opperated system that is controled by a vacuum switch on the transfer case and an acuater under the battery tray to pull the cable with the froce of the vacuum from the transfer switch engine vacuum . If you have an electronic shift control inside the cab it still works basicaly the same way except you have another electrical switch to check. It dosn't sound like you have a big problem because the system works it goes into 4 wheel but you need to find out witch part or switch is sticking mechicaly or if its an electrical switch sending or not sending the correct signial to its compontets

try selecting two wheel or four wheel high and reverse
truck in might come out for you

CODE PO650 MALFUNCTION INDICATOR LAMP CIRCUIT MALFUNCTION CONDITIONS. POSSIBLE CAUSES MIL CONTROL CIRCUIT IS OPEN , SHORTED TO GROUND TO SYSTEM POWER,MIL CONTROL POWER CIRCUIT OPEN IN THE INSTRUMENT CLUSTER, MIL THE LAMP IS DAMAGED OR HAS FAILED,INSTRUMENT CLUSTER OR THE PCM HAS FAILED. CODE PO332 KNOCK SENSOR CIRCUIT LOW INPUT BANK 2 CONDITIONS, POSSIBLE CAUSE KNOCK SENSOR FAILED, CODE P1875 4WD LOW SWITCH CIRCUIT MALFUNCTION CONDITIONS FOR TRANSMISSIONS 4L60E 4L80E, POSSIBLE CAUSES 4WD SWITCH LOW SIGNAL CIRCUIT IS OPEN OR SHORTED TO GROUND, 4WD LOW SWITCH IS DAMAGED OR IT HAS FAILED,PCM HAS FAILED.

Ckeck the acuator motor on the transfer case it may be burned out. With the key on (motor off) transmission in nutral try switching from 2 to 4 wheel drive and back you should hear the acuator moror run folowed by a click each time you activate the switch.

it is most likely your transfer case.if it is your front axle that is having problems .take it in to be checked