Hi my 99 blazers 4x4 isnt working the only button that lights up is the 4x4 and it flashes a couple times then fades out any ideas on how to fix it?

 

Look for threads on vacuum leaks and transfer case control modules (TCCMs). Those are the two places to start. Look for the symptoms for failure of each.

 

So if you go under the hood, near the firewall there's a vacuum switch in the center. One of the lines goes to your 4x4 vacuum actuator under your battery tray, The other goes to (if I'm not mistaken) the intake manifold and connects to a little port on the PCV hose. Inspect the lines and the actuator itself for holes and cracks.

My lines had holes all down it and dry rot. If that's the case for you, that's probably your problem. If it is, I would also check the vacuum lines for your HVAC system which is towards the firewall on the right fender (if you are viewing from the grill) right behind the ABS control module.

Here's a pic of one of my lines:


All my lines were like this because the factory heat shield is garbage.

Here is a quick guide on the locations I'm referring to:


However you should note that I own a 2001 Blazer LT with the 4 button 4x4 switch (Auto 4WD, 2HI, 4HI, and 4LO)