Notes On Intermittents

If Code EO12 is stored as a history code, start the engine and allow to idle while manipulating CKT 430 and 453. An intermittent open will cause the engine to stumble or quit when the ECM loses distributor reference signals. If the wiring and ECM connectors are OK, check the HEI pick-up coil leads for an intermittent open circuit, open or shorts on CKT 430 from distributor module to ECM, HEI module unable to process pick-up coil signals to produce distributor reference pulses.