With Single Sensor

DTC 43 Chart - Single Sensor:

Knock Sensor Circuit (Single):

CIRCUIT DESCRIPTION
The Diagnostic Trouble Code (DTC) 43 circuit consists of a knock sensor with one wire that goes directly to the Powertrain Control Module (PCM). There are two DTC 43 checks performed by the PCM. One check consists of monitoring CKT 496 for a voltage that is more than 4.3 volts and less than 0.64 volt.

DTC 43 WILL SET WHEN
If voltage is either too high or too low, for 10 or more seconds, DTC 43 will set.

ACTION TAKEN (PCM WILL DEFAULT TO)
The Malfunction Indicator Lamp (MIL) will illuminate.

DTC 43 WILL CLEAR WHEN
Conditions for fault are no longer present and Tech 1 scan tool "clear DTCs" function is used, 50 ignition switch keycycles have passed with no further faults, or ignition switch is turned "OFF" and ECM "B" fuse is removed for 10 seconds.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. The first test is to determine if the system is functioning at the present time.
2. Test two determines the state of the 5 volt reference voltage applied to the knock sensor circuit.

DIAGNOSTIC AIDS
The PCM applies 5 volts to CKT 496. A 3.9k ohm resistor in the knock sensor reduces the voltage to about 2.5 volts. When knock occurs, the knock sensor produces a small AC voltage that rides on top of the 2.5 volts already applied. An AC voltage monitor in the PCM is able to read this signal as knock and incrementally retard spark.
For further information, refer to Diagnosis By Symptom / Intermittents. - Intermittent Malfunctions