4WD won't fully engage- is there a module to replace?

What is your question?

4WD won't fully engage on '98 Cherokee with auto transmission. Is there a module or solenoid that needs replacing, if so where located? Thanx 4 your help.

What makes this problem better or worse?

Nothing- 4WD surges with Dash Lite that says 4WD partially engaged

How long has your 1998 Jeep Cherokee had this problem?

Since I bought the car Monday :]