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.

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 theses conditions are met for about 5 seconds, a code 43 will be set.




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. Code 43 will set:

^ Coolant temperature is over 90~C.
^ MAT temperature is over 0~C.
^ High engine load based on MAP and rpm.
^ Voltage on circuit 496 goes above 3.5 volts or below 1.5 volts.
^ All conditions met for 5 seconds.

If an audible knock is heard from the engine, repair the internal engine problem as normally no knock should be detected.

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.