2001 magnum 325 my 4×4 most of the time does not come on

I need help.
I own a magnum 325 2001 4X4. Now the 4×4 will not engaged all the time ( the light does not always turn on when I turn the switch), i can turn it on for a while then it stop working. I own the 2001 magnum 325 4×4 HDS wiring diagram but for some reason the wiring for the 4×4 is missing. I need to know were the gray/white is connected to? ( CDEF connecting wires are missing on the throttle assembly cover).
Were could be my problem? the brown wire is ground and it is fine, the black wire come from the main key switch and it is fine, the small wires are all ok ,I tested them. The power is coming throw the black wire?
Thank you very much