If this has already been discussed I apologize in advance. I couldn't find anything related to my issue specifically. I have an 02 s10 blazer and if I push the 4wd auto button it puts the truck into permanent 4wd. The service 4wd light comes on. I have checked the regulator under the battery and it works fine and I also replaced the 4wd brain. My transfer case does not have the vacuum switch. Any ideas on what to do to fix this would be much appreciated. Thanks

 

So you know that the front axle us being engaged which would indicate that there is no vaccuum leak?

Is yes to above, then is the transfer case control module could be bad. It is not uncommon for these to go bad.

If not the TCCM there is another switch in the transfer case but I'm not familiar with that part.

 

If you are simply judging really being in 4wd by the front axle locking and binding during rolling when the front wheels are turned - then you need to know that is normal. Auto 4WD locks the front axle shafts together 100% of the time so you feel that binding with the wheels turned, but in Auto the TC does not apply the power to the front wheels unless it detects wheelspin.

As far as the service 4WD light, you need a code reader that will read the TCCM codes for that. I would not jump to conclusions.

 

I replaced the TCCm about 3 months ago. So I am hoping thats not bad. I will have to research what the other switch is and its location and hopefully that is the problem. Thank You.

 

I have to check to see if my code reader does the TCCM codes if not I will have to take her to a shop. Thanks