Code E043, Electronic Spark Control (ESC) Circuit: Notes

The knock sensor is used to detect engine detonation. The ECM will retard electronic spark timing based on the signal being received. The circuitry within the knock sensor causes the ECM's supplied 5-volt 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 signal frequency are dependent upon the knock level.

If circuit No. 496 becomes open or shorted to ground, voltage will either go greater than 3.5 volts or less than 1.5 volts. If either of these conditions are met for about 5 seconds, a Code E043 will stored.

NOTE: Test numbers refer to test numbers on diagnostic chart.

Test Number 1) Code E043 will set if:

Voltage on circuit No. 496 goes greater than 3.5 volts or less than 1.5 volts
All of above conditions met for 5 seconds

If an audible knock is heard from the engine, repair internal engine problem. Normally, no knock should be detected at idle.

Test Number 2) If tapping on engine lift hook does not produce a knock signal, try tapping engine closer to sensor before proceeding.

Test Number 3) The ECM supplies 5 volts through a pull-up resistor. A reading of 4-6 volts should be present at knock sensor terminal.

Test Number 4) This test determines if knock sensor is faulty or if ESC portion of the MEM-CAL is faulty.