Skylark L4-138 2.3L DOHC VIN D MFI QUAD 4 (1989)
Ignition Control Module: Description and Operation
Electronic Spark Control (ESC)
Electronic Spark Control (ESC) is accomplished with a module that sends a voltage signal to the ECM. As the sensor detects engine knock, the voltage
from the ESC module to the ECM is reduced. This signals the ECM to retard the timing, if engine speed is over approximately 900 rpm.
