Powertrain Controls - ECM/PCM

DTC 43 Chart Knock Sensor Circuit:

Knock Sensor Circuit Wiring Diagram:

Circuit Description:

The knock sensor is used to detect engine detonation. The ECM will retard the spark timing based on the signal being received from the knock sensor. The knock sensor produces an AC voltage which is sent to the ECM. The amount of AC voltage produced by the knock sensor is determined by the amount of knock. 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.

There is one internal ECM test ran on this circuit to determine it is operating correctly. If the test fails, a DTC 43 will set.

If CKT 496 becomes open or shorted to ground, the voltage will either go above 4.12 volts or below 0.78 volts. If either of these conditions are met for about 5 seconds, a DTC 43 will be stored.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. If the conditions for the test, as described above, have been met, the scan tool will always indicate "NO" when the knock signal position is selected. If an audible knock is heard from the engine, repair the internal engine problem, as normally no knock should be detected at idle.

2. The ECM supplies 5 volts on CKT 496 which should be present at the knock sensor terminal.

3. This test determines if the knock sensor is faulty or if the IC portion of the PROM is faulty.

Diagnostic Aids:

Check CKT 496 for a potential open or short to ground. Also, check for proper installation of the PROM. - Intermittent Malfunctions