Code 43 - ESC: Notes

The knock sensor is used to detect engine detonation and the ECM will retard the electronic spark timing based on the signal being received. The circuitry within the knock sensor causes the ECM 5-volt reference 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. The amplitude and signal frequency is dependent upon the knock level. If circuit No. 496 becomes open or shorted to ground, the voltage will either go to greater than 3.5 volts, or less than 1.5 volts. If either condition occurs, Code 43 will be stored.

1. Determines if conditions for Code 43 exist (voltage on circuit No. 496 greater than 3.5 volts or less than 1.5 volts). The system is designed to retard spark 6 degrees if either condition exists.
2. The ECM applies and monitors 5 volts on circuit No. 496. This voltage should be present at the knock sensor terminal.
3. Determines if knock sensor resistance is between 330-4500 ohms, sensor is okay.
4. If circuit No. 496 is not open or shorted to ground and the voltage reading is less than 4 volts, the most likely cause is an open circuit inside the ECM. If a replacement ECM did not repair the problem, it is possible a faulty MEM-CAL is drawing the voltage down and should be replaced.