Based on all posts you have made in this thread, I missed nothing. You presented your problem very poorly - and going into/out of 4LO is definitely not where to start diagnosis. I decided to start from scratch and asked you to do specific tests in a clear and concise manner. You still have done nothing to indicate you have done the tests as I asked, and refer me to the same poorly presented information previously given (and you keep doing this). You are welcome to go elsewhere for your answers if you don't like mine. This is the last post I will be making in this thread.

 

I presented exact descriptive answers in a quoted text of all of your questions line by line. I even removed said answers from the quoted text so you could clearly see the responses. I told you to look at your quoted text that contains the test results of me walking out to my garage and doing the exact thing you outlined in the quoted text. If you cannot figure that out I do not think we have the ability to communicate.

Even though you "aren't going to reply anymore" I'm going to try one last effort to make it really - really simple for you.

-Now your questions are going to be listed - and then the test result? Still with me? I hope :/

Your Question: Is the Service 4WD light on?

My Answer: Service light not on

Your Question: With vehicle in 2WD HI, jack up the passenger front wheel off the ground. Leave the drivers side on the ground. Start engine (leave in park). Can you rotate the wheel that is off the ground by hand. Is the 2WD light on steady?

My Answer: The wheel freely turns. 2wd steady - THIS MEANS THE LIGHT IS ON ALL THE TIME NO FLASHY FLASHY - OH THE TRUCK IS ON A JACK

Your question: Now push the 4WD HI button. What happens? Is the 4WD light on steady? Can you rotate the wheel that is off the ground by hand?

My Answer: Push 4hi and hear a relay click sound from passenger side interior along with an electronic sound underneath the driver door area. 4hi button does not stop flashing (still in park) even after over a minute. Wheel still rotates. - VEHICLE NEVER LEFT PARK EVEN THOUGH IT SAYS STILL IN PARK IT NEVER CAME OUT OF PARK DURING THESE TESTS - IT STILL SAYS P ON THE SHIFTY THING THAT MAKES IT GO BACKWARD AND FORWARD

Your Question: Now push the 2WD Hi button again. What happens? Is the 2WD light on steady? Can you rotate the wheel that is off the ground by hand?

My Answer: Hear relay click again and 2hi light goes steady. Wheel rotates

If you honestly cannot understand how I have gone out, done your tests and reported back to you then I cannot help you and I don't think anyone can.

All of this was listed posts and posts ago while you continue to pretend this information does not exist in this thread. Try READING NEXT TIME Post #16 and Post #20 CONTAINS ALL THE ANSWERS TO THE TESTS YOU ASKED FOR

 

In retrospect I can see how the questions were answered by your typing in the quoted section. Kind of a strange way I think to put response in with the greyed quote, but it WAS there so I was wrong. Since you did what I asked and reported I think I owe you a response. You can use it if you want (or not). For the record, I think we were both buttheads so I'm not going to apologize.

Your front axle is definitely not locking in (which really operates independently of the transfer case). When you push the button, the TCCM commands the TC encoder motor to move the selector shaft to 4WD and also energizes the vacuum solenoid on the firewall to apply vacuum to lock in the front axle. There is a sensor on the axle that tells the TCCM when it has locked. There is a sensor in the encoder motor that tells the TCCM what position the selector shaft is in. When both sensors indicate to the TCCM that the new positions have been attained, the TCCM will stop flashing the 4WD light in the selector switch and it will be on steady. I suspect the lack of front axle lock is causing the TCCM to reject the 4WD selection and it simply returns to 2WD after waiting for the time period. The return to previous mode is known behavior when shift is incomplete.

1) Do you have vacuum to the solenoid on the firewall?
2) Do you have vacuum through the solenoid to the actuator under the battery tray when 4WD is flashing?

I'm going to assume that you do. If not please advise.

Does actuator bellows pull on cable when vacuum is applied? Do bellows leak vacuum or will it hold vacuum? If bellows pulls back, how far? The cable should move 1/2" to 3/4" when pulled by the actuator (or by hand). If operation of actuator seems normal and wheel still won't lock, front axle locking mechanism will need repaired.

Once you have the front axle locking in, I suspect the 4WD light will stay on steady and all will be fine. If not please advise. Keep in mind that you could possibly have more than one problem.

If bellows won't release when going back to 2WD, switch the hoses on the vacuum solenoid on the firewall (only one side is vented).

FYI my Blazer is also a 2001 4-button rig and I am thoroughly familiar with this system from repairing my own.