DTC 43

Code 43 Chart:

Code 43 Wiring Diagram:

CIRCUIT DESCRIPTION:

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 volts to be pulled down so that under a no knock condition, circuit 496 would measure about 2.5 volts. The knock sensor produces an AC signal which rides on 2.5 volts DC voltage. The amplitude and frequency is dependent on the knock level. If circuit 496 becomes open or shorted to ground, the voltage will either go above 3.5 volts or below 1.5 volts. If either of these conditions are met for about 1/2 second, a Code 43 will be stored.


NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to ECM CONNECTOR IDENTIFICATION under ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS for correct color code identification of circuit.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. This step determines if the condition for a Code 43 still exist (voltage on CKT 496 above 3.5 volts or below 1.5 volts). The system is designed to retard the timing 15~ if either condition exist.

2. The ECM has a 5 volt pullup resistor, which applies 5 volts to circuit 496. The 5 volt signal should be present at the knock sensor terminal during these test conditions.

3. This step determines if the knock sensor resistance is 3000 to 4500 ohms. If it is, the sensor is ok.

4. If circuit 496 is not open or shorted to ground and the voltage reading is below 4 volts, the most likely cause is an open in the ECM. It is possible that a faulty Mem-Cal could be drawing the 5 volt signal down, and it should be replaced if a replacement ECM did not correct the problem.


DIAGNOSTIC AIDS:

Check circuit 496 for a potential open or short to ground. Also, check for proper installation of Mem-Cal.

Refer to TESTING PROCEDURES/DIAGNOSIS BY SYMPTOM/INTERMITTENTS.