DTC 43

Code Chart 43:

Knock Sensor Circuit:

CIRCUIT DESCRIPTION:
The knock sensor is used to detect engine detonation, and the ECM will retard the Ignition Control (IC) 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, 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 is dependent upon the knock level.

If CKT 496 becomes open or shorted to ground, the voltage will either go above 4.6 volts or below .64 volt. If either of these conditions are met for about 10 seconds, a DTC 43 will be stored.

TEST DESCRIPTION: Number(s) below refer to circled number(s) on the diagnostic chart.

1. This step determines if conditions for DTC 43 still exist (voltage on CKT 496 above 4.6 volts or below .64 volt). The system is designed to retard the spark 15°, if either condition exists.

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

3. This step determines if the knock sensor resistance is 3900 ohms + 15%. If the resistance is between 3300 to 4500 ohms, the sensor is OK.

DIAGNOSTIC AIDS:
If CKT 496 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 PROM could be drawing the 5 volt signal down and it should be replaced, if a replacement ECM did not correct the problem. - Intermittent Malfunctions Knock sensor case is the ground. DO NOT use teflon tape, anti-seize compounds, or sealants.