C 1500 Truck 2WD V6-262 4.3L VIN Z TBI (1995)
Dual Knock Sensor Circuit
CIRCUIT DESCRIPTION
The Knock Sensor (KS) system consist of two knock sensors with one wire that goes directly to the control module. There is a KS check
performed by the PCM. The check consist of monitoring CKT 496 for a voltage that is more than 0.63 volt and less than 3.1 volts.
If the voltage is either too high or too low for 10 or more seconds, DTC 43 will set. The PCM uses this self check only.
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.
3. Test 3 determines the state of the knock sensors and connections themselves.
DIAGNOSTIC AIDS
The control module applies 5 volts to CKT 496. A 8200 ohm resistor in the knock sensors 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 control
module, 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
