I have read some threads can't seem to find one with the same issues... I have 2000 blazer ls 2 door. Front driveline was out when I bought it so I went and got a driveline and transfer case just in case either one was bad. Well I finally got the driveline in which was a major project ha. But 4wd won't engage or do anything. No lights come on the 4wd switch when I press them. But if I pull fuse and put it bavk in they light up and flash service 4wd then it goes away... just replaced all vacuum hoses haven't got to the actuator yet. But could it just be a bad 4wd switch. One of the buttons is broken and pushed in... also I pulled the bottom vacuum line on that electric vacuum switch that runs down to my actuator buy have no vacuum pressure.. plz help thanks

 

Update pulled vacuum lines from solenoid on firewall and connected them bi passing the solenoid. And it went into 4hi. Corrosion on tccm cleaned that up and now can't get it out of 4hi without plugging vacuum line....