Electronic Spark Control (ESC)

The ESC system consists of a knock (detonation) sensor and the MEM-CAL portion of the ECM. The ECM supplies and monitors a 5-volt DC reference signal on the knock sensor signal line. Internal circuitry of the knock sensor will pull this voltage down to about 2.5 volts. When knock occurs, the knock sensor produces an AC voltage signal which rides on the 2.5-volt DC signal. The voltage and frequency of this signal depend upon knock signals received by the sensor. The ECM will retard spark timing until signals from detonation sensor cease.