I have a 2001 jimmy and when I try to put it into 4wd hi or low or auto the light just blinks. I have searched for stuff to check and I found a vacuum line going to the actuator that the end looked bad I cut the bad off and ran it a different way since it was shorter since I don't have any new hose right now and still nothing. I have checked all fuses, disconnected the battery for an hour, pulled the 4wd fuse for 10 minutes because I saw that will reset the tccm, and still nothing. I hear clicks on the passenger side inside next to the door and checked the plugs there and listened and hear clicks in the transfer case going from 2wd to 4wd hi but it's just not clicking in. What should I check next

 

You will need to check the vacuum actuator and actuator valve. Check you are getting 12 volts to the connector when in 4WD. If OK, bypass the valve, which is mounted on the engine bulkhead center above the distributor, by pulling the two lines off and using a vacuum hose coupler, link them together. If that makes the 4WD work the valve is bad. If not, you will need to check the actuator which is mounted on the front axle. You can gain access by removing the battery and tray. The diaphragm can split, they can seize up. The cable from the actuator to the front axle clutch can break, seize etc.
Good Luck!

 

Thanks for the reply! I actually finally figured it out yesterday and it was the actuator valve I bypassed it and it worked and hooked it back up and tapped on it with a wrench and everything is good now. I'm gonna order that new to keep in the glove box if it ever happens again but I also saved a piece of plastic tubing I found that I can connect the two vacuum lines in an emergency. I wish I would have known that's all it was it would have saved me a lot of time over the weekend trying to figure out what was wrong and worried about the snow we just had here on the east coast and having no 4wd