Vehicle; 1996 Chevrolet. C/K truck (Cheyenne 3500 ) w/5.7 liter engine. vin code ( R ) Problem;; No spark at plugs . Tested crankshaft position sensor, ignition coil driver, ignition coil, and all circuits for voltage and continuity, between components. The distributer rotor is turning. No soon lite and scanner cannot communicate with V C M What else other than the V C M could cause this problem ?