Pickup 4WD V6-3137cc 3.1L (CPC) (1993)
Voltage Signal: Description and Operation
Ignition Reference Pulses
HEI / DI Module
PURPOSE
Informs the ECM of engine position.
LOCATION
Within the distributor housing.
OPERATION
To provide RPM and crank position information, a distributor reference signal is sent to the ECM from terminal "C" of the HEI/DI module. The
ECM uses the distributor reference signal as the basis for its calculation of spark advance required at any given moment. If base ignition timing is
incorrect, the entire spark curve is incorrect.