ok 99 so blazer..if i push any button except 2wd the button that is pushed will blink..i think its a vacuum leak..u can hear it try to engauge but wont spin the front tires..i dont know what else it could be..and there is no service 4wd light

 

3-button or 4-button switch on the dash? Have you tried holding the button for the desired mode?

If 3-button, check out the OBD2 Non-Automatic Transfer Case Diagnosis thread in the Tech Article (DIY) section (check the links in my signature for the tech article index).

Regardless of 3-button/4-button, you can remove the battery and check for vacuum at the front axle when you select a 4wd mode.

A vacuum problem may not necessarily prohibit the shift into 4wd.

You can also check the TCCM (behind the passenger side kick panel) and the Encoder motor (on the transfer case) electrical connections for signs of corrosion. Any corrosion on these connectors can result in bad signals to/from the TCCM and result in an incomplete shift.

 

its 4 button with auto 4x4 and yes tried hold u can hear the transfer case lock in..but it still aint workin..you can hear the relay or whatever on the pass side clickin..

 

so i got it all apart and i think its a vacuum leak..if i squeeze the pump i can hear air leakin from a line somewhere ...so gonna replace it and see what happens

 

also with the line unhooked i feel very little pressure...

 

are you putting it in neutral then changing? Might be a stupid question but some people dont realize they have to do that. Yes it is push button 4wd but you still need to engage it in neutral.

 

yes it was in neatural

 

i hope it was just a leak, keep us updated

 

vacuum leak it was thank god with two feet on the ground and 2 more comin...it was the line that goes from the pass side to under the cowl.....works like a champ now..thank god i gotta work tonight and a little piece of mind knowing it works