High Energy Ignition (HEI) System - TBI

The Electronic Spark Control (ESC) system module sends a voltage signal (8 to 10 volts) to the ECM when no spark knocking is detected by the ESC knock sensor, and the ECM provides normal spark advance. When the knock sensor detects spark knock, the module turns "OFF" the circuit to the ECM (0 volts). The ECM then retards EST to reduce spark knock.