System Diagnosis - Knock Sensor (KS)

Knock Sensor (KS) System Check:

Knock Sensor (KS) System Circuit:

CIRCUIT DESCRIPTION
The Knock Sensor (KS) system consist of two knock sensors with one wire that goes directly to the Powertrain Control Module (PCM). The PCM check consists 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 16 or more seconds, Diagnostic Trouble Code (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.
3. This diagnosis CKT 496 and the knock sensor.

DIAGNOSTIC AIDS
The PCM 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 PCM, is able to read this signal as knock and incrementally retard the spark.