DTC 43

Code 43 Chart:

Code 43 Wiring Diagram:

CIRCUIT DESCRIPTION:


The knock sensor detects engine detonation and the ECM retards the electronic spark timing based on the signal being received. Under a no knock condition, the circuitry within the knock sensor causes the ECM 5 volts to be pulled down so that CKT 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 496 becomes 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 set.


TEST DESCRIPTION: Number(s) below refer to circled number(s) 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 3300 to 4500 ohms. If it is, the sensor is ok.

DIAGNOSTIC AIDS:

- If circuit is not open or shorted to ground and the voltage reading is below 4 volts, the most likely cause is an open circuit 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.