hey guys my 4wd does not work so I'm going to replace the parts one by one until it is fixed what part do you think I should replace first, and where is it located. 98 chevy blazer. the 4hi light comes on when I push the button and I hear a clicking sound under the truck but it does not engage. Thank you

 

Do you have auto4wd? or just 4HI, 2HI, 4LO?

Just replacing parts one at a time is never a good idea...

 

i have 4hi 4low and 2hi buttons

 

Check out this article to check for stored codes in the TCCM:
OBD2 Non-Automatic Transfer Case Diagnostics

Let us know what that returns, if anything.