My truck is stuck on 4HI it will not shift into 2HI what can I do

Potential causes to consider:

Transfer Case Actuator (TC Motor): The transfer case actuator, also known as the TC motor, is responsible for engaging and disengaging the transfer case. If it's malfunctioning or stuck, it can lead to issues like the one you're experiencing. Consider checking the actuator for any signs of damage or water ingress.

Transmission in Neutral: When shifting from 2Hi to 4Hi, ensure that your transmission is in neutral. Some vehicles require this step to engage the 4Hi mode successfully. Try shifting to neutral before selecting 4Hi2.

Rolling Movement: Another technique is to roll the vehicle slowly (forward or reverse) while attempting to engage 4Hi. Sometimes, this movement helps the transfer case engage properly. Give it a try and see if it resolves the issue.

Transfer Case Control Module: The transfer case control module (TCCM) manages the transfer case functions. If it's faulty, it might prevent successful mode changes. Diagnosing and testing the TCCM using a high-end scan tool (like a Tech 2 or Snap On) could be necessary.

Indicator Switch on Front Axle: If the 4Lo mode isn't engaging, check the indicator switch on the front axle. Sometimes, manually pushing it in while the connector is plugged in can help troubleshoot the issue.

Remember that diagnosing these issues may require professional assistance or specialized tools.

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.

Put truck in Neutral while key in run position engine off or on (doesn't matter which). If it's pushbutton 4wd then try hitting 4low again. if that doesn't work some of the chevy trucks required you to press 4hi to get into 4high and then press 4hi again to get back to 2hi, unless yours has a 2hi button. In that case press 4hi to get into 4high and then press 2hi to get back to 2wd. either way you need to be in neutral to get out of 4lo. I have shift on the fly (Mechanical Shifter on floorboard for transfer case) on my 1990 Suburban and still have to put it in neutral to get out of 4lo. Good Luck.

• Shifting from 2HI to 4HI Press and release the 4HI button. This can be done at any speed, and the front axle will lock automatically.

• Shifting from 4HI to 2HI Press and release the 2HI button. This can be done at any speed, and the front axle will unlock automatically.

• To shift from 2HI or 4HI to 4LO, the vehicle must be stopped or moving less than 3 mph with the transmission in NEUTRAL

• Hope this helps.

sounds like a bad acuator drop by a AAMCO they can diag it and give a free quote too

Try commanding the drive ranges while in netural cycling them. This may normalize the controller that senses the position from the encoder motor assembly. There maybe a procedure for that in a service manual.

You should be able to put in 4x4 while in drive less than 35mph. Mine had a switch to turn to engage or dis-engage.

Replace the selector switch assembly. Common failures.

A good ground is very imporant on these vehicles

it is either the control switch or the actuator. look if light is flashing on push button switch. if so it is stuck. you can check actuator on front axle, to watch and see if it is moving.