C 1500 Truck 2WD V8-350 5.7L VIN K TBI (1995)
Knock Sensor Circuit
CIRCUIT DESCRIPTION
The Knock Sensor (KS) system consist of a knock sensor with one wire that goes directly to the PCM. There is a check performed by the PCM.
The check consist of monitoring CKT 496 for a voltage that is more than 0.04 volt and less than 4.6 volts.
If the voltage is either too high or too low for 16 or more seconds, DTC 43 will set.
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 3900 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.
If the KS system checks OK, but detonation is the complaint, refer to Diagnosis By Symptom / Detonation, Spark Knock See: Testing and
Inspection/Symptom Related Diagnostic Procedures/Detonation/ Spark Knock
