Chart C-5, Electronic Spark Control System Check: Notes

Electronic Spark Control (ESC) is accomplished through a knock sensor that modifies a voltage sent by the ECM under detonation conditions. As the knock sensor detects engine knock, the voltage in circuit No. 496 drops from 5 volts to approximately 2.5 volts. This is sensed by the ECM and spark timing is modified.

1. With the engine idling, there should be no knock signal present.
2. Tapping the lift hood bracket should simulate a knock signal to determine if the sensor is capable of detecting detonation. If no knock is detected, try tapping on the engine block closer to the sensor, before replacing sensor.
3. If the engine has internal problems which are creating the knock, the sensor may be responding to internal failure.
4. This test determines if the knock sensor is faulty or if the ESC portion of MEM-CAL is faulty. If the MEM-CAL is suspected, be sure that it is properly installed and latched in place.