Blazer will not shift into 4 hi or 4 lo. 4 hi button blinks and goes back to 2 hi. Tried disconnecting battery, but same issue after reset. Checked wires at TCCM, but seem okay. What is bad? TCCM?

 

3-button or 4-button 4wd dash switch?

 

3 button

 

the computer sees that the transfer is not completing a shift. can be mechanical or electrical problem. encoder motors are known to go bad.

 

Before you assume the encoder motor is the problem, run through the proper testing. Start with getting the codes from the TCCM (OBD2 Non-Automatic Transfer Case Diagnostics). It could be corrosion at the encoder motor. It very well could be an encoder fault, but it is easy enough to check the codes.

 

I just bought a 99 Blazer a couple hours ago with this same problem. Mine has the 3 button switch.

#15 Fuse keeps blowing out (for the 4x4).

What does TCCM stand for ??

I assume the encoder motor is which does the actual shifting in the transfer case ?

 

TCCM == Transfer Case Control Module

It is the brains in the 4wd system. It is located behind the passenger front kick panel.