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Home >> GMC >> 1994 >> Forward Control 4.3 Z, Standard >> Repair and Diagnosis (Single Page) >> Engine Performance >> Theory and Operation >> Engine Controls - Theory & Operation - Gasoline >> Computerized Engine Controls >> Input Devices >> RPM Reference Signal
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RPM Reference Signal

PCM monitors RPM through ignition module tach/pulse signals (on circuit No. 430) produced by the HEI module (RPM reference line of 4-wire EST connector). PCM uses signal to determine control of timing, fuel delivery (fuel pump relay energizing), EGR function and idle speed. PCM also uses signal to trigger fuel injectors.

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