I got a 2001 blazer, when I try to go into 4x4 high or low the light goes solid the truck thinks it's locked into 4x4 but it is not. What would that issue be? I was told it might be the actuator on the diff it self.

 

There are several possible issues. Two of the most common are the Transfer Case Control Module (TCCM) located behind the passenger side kick panel and rotted vacuum lines that leak disabling the front axle engagement.

For the TCCM, these can go bad and before they do you will here repeated clicking from the kick panel as it tries to engage the transfer case. There can also be corrosion on the electrical connector to it.

If you have access to a good OBD scanner, you might be able to pull some codes to help with the diagnosis. An auto parts store can often do that for you.

 

I'm not throwing any codes and I do hear the clicking but only once like I want to say "normal" so im assuming its a vacuum leak somewhere?

 

If the TCCM only clicks once, then it is likely fine.

The next easy thing to check is the vacuum supply to the front axle actuator.

The underhood vacuum lines can dry-rot and leak.

Do you have the three or four button transfer case control panel?

 

This is a tech article I submitted that shows the vacuum hose layout for the 4-button transfer case.
https://blazerforum.com/forum/articl...po-np8-107011/

 

I have 3 button t-case control

 

I've attached some pdfs I've downloaded that show the vacuum hose routing for the 3-button systems. The hoses that are most likely to have rotted are the ones that go from the engine to the Tee/one-way valve, to the vacuum reservoir, and to the HVAC system. These are hoses 33 (both) and 30 in the file "BLAZER 4WD - Actuator & controls_front axle_ 3-button _ Chevrolet EPC Online _ Nemiga.com". These will be located between the upper intake plenum, running under the air intake hose for the throttle body, between the power brake diaphragm and the ABS module, and into the fender where the vacuum reservoir(29) is located. The one-way valve/Tee is number 32.

Hopefully all you have is bad vacuum lines as these are easy to fix.

 

thank you! I appreciate it