DTC 43

Knock Sensor Circuit Diagram:

CIRCUIT DESCRIPTION:
The knock sensor is used to detect engine detonation and the PCM will retard the electronic spark timing based on the signal being received. The circuitry within the knock sensor causes the PCM'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 bias. The amplitude and frequency of the knock signal is dependent upon the intensity of the noise.

Code 43 will set if CKT 496 becomes open or shorted to ground (indicated by signal voltage greater than 3.5 volts or below 1.5 volts) for 20 seconds or more.

TEST DESCRIPTION:

Code 43 Diagnostic Chart:

Numbers below refer to circled numbers on the diagnostic chart.

1. If a Code 43 is detected, the PCM 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 PCM applies 5 volts to the knock sensor circuit (CKT 496) which is reduced to approx. 2.5 volts by a resistor to ground, in the sensor. With the sensor disconnected, the measured circuit voltage should be the applied voltage (5 volts) from the PCM.
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 too close to secondary ignition wires, it may induce a voltage and cause a false knock signal.