Electronic Spark Control System (ESC)

There are 4 basic components to the ESC system: A detonation sensor, a HEI-EST distributor, an ESC controller, and the ECM. When detonation (engine knock) occurs, the detonation sensor sends an electrical signal to the ESC controller. The ESC controller amplifies this signal and transmits it to the ECM. The ECM will then retard spark timing until the ECM no longer receives a signal from the detonation sensor.

Fig 1: Schematic of Electronic Spark Control System

NOTE: For more information on operation and testing of the HEI-EST system, see GENERAL MOTORS COMPUTER COMMAND CONTROL in 1985 COMPUTERIZED ENGINE CONTROLS Section.