Motor turns but wont start. on 1996 Jeep Cherokee

There is no volt going thru nun of the two wires that plugs in to the coil when i turn the switch to on, need to know why and what do thanks.
All the fueses are good

Asked by for the 1996 Jeep Cherokee
one wire has 12 volts with the key on. the other wires goes back to the computer and grounds and ungrounds the coil for spark. the crank sensor controls that pulse and may be at fault. have it checked for failure at a shop.

Where dose the 12 volt come from?
the 12 volt is missing.
ignition switch with the key in the on position