Suburban 3/4 Ton 4WD V8-305 5.0L (1986)
Engine Speed Signal: Description and Operation
On all models with full function systems except V6-229 (1983 - 84 VIN code 9) engines, the ``R'' terminal on the 7 terminal ignition module provides
reference pulses to the ECM indicating engine RPM and crankshaft position.
