Powertrain Controls - ECM/PCM

Code 43 Chart:

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 5.0 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 AC signal which rides on the 2.5 volts DC voltage. The amplitude and signal frequency is dependent upon the knock level.

Code 43 will set:

If CKT 496 becomes open or shorted to ground, the voltage will either go above 3.5 volts or below 1.5 volts.

All conditions are met for 20 seconds.

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 a Code 43 is detected, the ECM will retard spark timing by 10 degrees. If an audible knock is heard from the engine, repair the internal engine problem. Normally no knock should be detected at idle.

2. The ECM has a 5.0 volt pull-up resistor which should be present at the knock senor terminal.

3. 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 intermittent open or short to ground. Also check for proper installation of Mem-Cal. If ESC circuit 496 is routed to close to secondary ignition wires, it may induce a voltage and cause a false knock signal. Refer to TESTING PROCEDURES/DIAGNOSIS BY SYMPTOM/INTERMITTENTS.