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's supplied 5 volt signal to be pulled down, so that under a no knock condition CKT 496 would measure about 2.5 volts. The knock sensor produces an A/C signal which rides on the 2.5 volts DC voltage. The amplitude and signal frequency is dependent upon the knock level.

There are two test run on this circuit to determine if it is operating correctly. If either of the test fails, a Code 43 will be set.

a. 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 two conditions are met for about 1/2 second a Code 43 will be stored.

b. This system also performs a functional test to determine if the knock sensor is responding to engine detonation. To perform this test, the ECM will advance the spark under certain load conditions and look for the knock signal response. If knock is detected before conditions are met to run the test, the test is bypassed, but if the test run and no knock is detected the Code 43 will be set.

This test is performed when:

^ Coolant temperature is over 90~C.
^ MAT temperature is over 0~C.
^ High engine load based on air flow and rpm between 3400 and 4400.



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. If the conditions for for the A test, as described above, are being met the "Scan" tool will always indicate "yes" 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. If tapping on the engine lift hook does not produce a knock signal, try tapping engine closer to sensor before proceeding.


3. The ECM has a 5 volt pull-up resistor which should be present at the knock senor terminal.


4. This test determines if the knock sensor is faulty or if the ESC portion of the Mem-Cal is faulty.

DIAGNOSTIC AIDS:


^ Check CKT 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.

If the customer's complaint is the "SERVICE ENGINE SOON" light comes "ON" when in acceleration, the B portion of this Code is failing. There is a possibility that the Direct Ignition System was in bypass mode when the 43 test was run. An intermittent open in the EST circuit will put the DIS module in the bypass mode which will not allow the spark to be advanced so the 43B test would fail. If ECM also had a 42 stored, then the EST circuit is likely the cause of the Code 43.