Hello, I have a 2002 blazer 4x4 LS 4 door, 4 button 4x4. I have the same prob with 4x4 as other, lights just flash. I check the actuator and I realized it didnt have enough vacuum to pull the cable to engage 4x4. I traced the vacuum line to a relief valve on the firewall, then two lines from the valve. One line goes over the brake booster, and into a 3 way t. I see one of the hoses going into a smaller plastic line and going under the vehicle (i think). The other hose is disconnected, and constantly sucking air while engine is running. I am sure that this is my problem, but I have no idea where this hose goes. The fender was off recently, and my guess is the person didnt hook it up. Please please please help, i really appreciate it.

 

From your description this sounds like the line that should connect to your vacuum cannister. It should be located near the front of the engine compartment if memory serves. It could very well have gotten disconnected when the fender was taken off.

 

are you talking the actual one that goes into the fender. that's the reserve for WOT conditons when engine vac is low

 

It has to be going to the one inside the fender, the hose isnt long enough to go anywhere else. I hooked it up but it still wont go into 4x4. Im getting desperate, i just dont know whats going on. I can unhook the cable from the actuator, pull it manually and it goes into 4x4.

 

well that wouldn't stop your 4wd from working. only if you had your foot to the floor and you were trying to engage 4wd.

 

Its fixed! I replaced the sensor mounted on the front rear end ( right where the cable on the other end of the actuator goes ) I sold it 3 hours later! Huzaah! Thanks for all the help and posts, great forum!