Chart C5 - ESC: Notes

The Electronic Spark Control (ESC) system is used to detect engine detonation. The ECM will retard the Electronic Spark Timing (EST) based on the signal being received from the knock sensor. The circuitry within the knock sensor causes the ECM's 5-volt reference signal to be pulled down so that under a no knock condition, circuit No. 496 would measure about 2.5 volts. The knock sensor produces an AC signal, which rides on the 2.5 volts DC voltage. The amplitude and frequency are dependent upon the knock level.

The Mem-Cal used with these ECM applications contains the functions which are part of the remotely mounted ESC modules used on "F" and "Y" Body vehicles. The ESC portion of the Mem-Cal sends a signal to other parts of the ECM which retards the spark timing to eliminate detonation.

1. With engine idling, there should be no knock signal present at the ECM because detonation is not likely under a no load condition.
2. Tapping the engine hook bracket should simulate a knock signal to determine if the sensor is capable of detecting detonation. If no knock is detected, try tapping the block closer to the sensor.
3. If the engine has an internal mechanical problem which is creating knock, the knock sensor may be responding to the internal mechanical failure.
4. Test determines if the knock sensor is faulty or if the ESC portion of the MEM-CAL is faulty. Be sure the MEM-CAL is properly installed and latched in place.