4.3L Turbo & Models With 4L80-E Transmission

ECM/PCM applies and monitors a 5-volt DC signal to the knock sensor. Internal knock sensor circuitry pulls this DC signal down to about 2.5 volts. When knock sensor detects detonation, it generates an AC signal which rides back on the DC signal to the ECM/PCM. Knock signal intensity is dependent upon knock signal level.

NOTE: Test numbers refer to test numbers on diagnostic chart.

Code 43 will set when vehicle reaches normal operating temperature (but not overheating), high engine load is indicated by MAP sensor and voltage on circuit No. 496 is greater than 3.5 volts DC or less than 1.5 volts DC. This step determines if system is functioning properly at the current time.
This step determines the state of the 5-volt reference signal applied to the sensor.
Checks knock sensor internal resistance.

Fig 1: Code 43 Schematic (4.3L Turbo & Models W/4L80-E Trans.) Electronic Spark Control

Fig 2: Code 43 Flow Chart (4.3L Turbo & Models W/4L80-E Trans.) Electronic Spark Control