Bought the Arizona ride in super clean shape that had been in Michigan for 2 years , everything is A1 the seller stated he had too change some bad vaccum lines and cv shafts on the 4wd due too AZ weather causing issues with the vaccum lines and everything worked fine for him that year (Supposedly ) imho I don’t know how much I believed . So he said he didn’t test the 4wd this last winter at all after the fix because he kept the blazer stored . So upon test driving etc and looking it over with a fine tooth comb / I engaged the 4wd drive the light on bezel changes from 2wd too 4wd HI and drove great in 4wd .

After we stopped at a light too switch Back into 2wd it stays in 4wd it makes the noise on the actuator back and forth and you can hear it when attempting too go back too any other drive mode. Eventually after steering it back forth and going forward and reverse it goes back into 2wd when it chooses .After all that mess the Abs light and brake light are on. I checked there are no Active codes except 1 .

(C0625 solenoid control monitor error )

His believability on actually fixing it the first round was half believable but it worked for the most part with my own two eyes , it just wont go back into 2wd he gave a shpeel on how this is likely a actutor or module issue easy fix? With that said I wanna know where I can likely start too look for this fix . If it’s too much I’ll just delete the cvs and make it 2wd permanent. That’s what I was looking for anyhow when I was out shopping for a blazer but if it has it I wanna use it .
thanks in advance

 

You'd be best to learn how the 4wd system on these Blazers works so you can best diagnose the issue.

For instance, there are two types of transfer cases, colloquially called the "3-button" and "4-button" types. The 4-button type also has the "Auto-4wd" option in addition to the 2hi, 4hi, and 4lo. These have different vacuum hose routings.

The vacuum hoses sere two purposes. For each type, vacuum is applied to a large actuator under the battery that pulls on a cable that engages the passenger side axle shaft of the front axle. The other vacuum hoses are associated with the control of the transfer case.

These vacuum hoses seldom last over 15 years. A symptom of them leaking is when the HVAC system doesn't duct the air flow to where you intend it to go. This is because it also uses vacuum to control the HVAC actuators.

As for other failure mechanisms, there is the transfer case control module (TCCM) that is located under the passenger side kick-panel. This has relays in it that can go bad. When it is failing, you will hear lots of clicking coming from there. Sometime the fix for this can be to clean the contacts to the TCCM, sometimes it needs to be replaced.

The other failure mechanism is in the transfer case where a solenoid can go bad.

If you are desperate to get the truck back into 2wd, you can try to disable the front axle engagement mechanism that is connected to the vacuum actuator under the battery. Because the front axle is no a locking one, even if the transfer case is engaged, the front axle won't bind if the passenger side axle shaft has been dis-engaged.

Hopefully this information will get you started on the diagnosis. Others might also chime in to help out too.