Electronic Spark Control Module: Description and Operation

To control spark knock, Electronic Spark Control (ESC) system has been added. This system is designed to retard spark timing up to 20 °, to reduce spark knock in engine.

ESC system has two major components:

^ ESC Module
^ ESC Knock Sensor

Knock sensor is mounted in engine block under intake manifold. When abnormal engine vibrations (spark knock) are present, sensor produces voltage signal which is received by Electronic Spark Control module. As long as ESC module sees no voltage from knock sensor, ESC sends a signal voltage (8 to 10 volts) to ECM which in turn provides normal spark advance.

When ESC module detects voltage from knock sensor, it turns "OFF" signal to ECM and voltage at terminal "D10" goes to 0 volts. ECM then retards EST to reduce spark knock.

ESC signal line has a shield wire to prevent false signals to ESC module. If shield wire loses its ground, a false Code 43 may result or ignition timing may retard
needlessly.