Zr2 4x4 problems 4 button
 

I bought a 99 ZR2 ( with 50000 miles) with 4X4 problems
I know there are problems with 4 button.
I can choose 4WD,4HI or 4LO when the I start the car and after few miles ( so no more than 3 or 4 times) but after nothing works
SO When I want 4WD, I can hear "click" from the TCCM , and noise under the body, button flash but going back in 2WD or if I was in 4LO going back in 4LO
I think I need to check vacuum line but after ?
thanks

I have a 4-button system too and made a thread on the replacement of the vacuum hoses. You might find it useful. It is in my signature.

As for the TCCM, do you hear repeated clicking sounds or just single clicks when a change in the 4wd settings is requested? If you hear repeated clicking, then the TCCM or the connection to it could be bad.

Thanks
only single click

I need to star a new thread because now the problem is only the 4LO button

99 zr2 4lo problem
 

the problem was that once the 4LO system was engaged, I could not go back. I had to wait until the next day to get back and I came back to 2HI.
now it's reversed, I can not go to 4LO. I hear a "clong" under the body ( I suppose from the tranfert case but nothing happens.)
I can only choose 4WD, 2HI or 4HI without problems.