System Diagnosis - Knock Sensor (KS) With VCM-A

Knock Sensor (KS) System Check:

Knock Sensor (KS) System Circuit:

CIRCUIT DESCRIPTION
The Knock Sensor (KS) circuit consists of two knock sensors with one wire that goes directly to the Vehicle Control Module (VCM-A). The Knock Sensor (KS) check performed by the VCM-A consists of monitoring Circuit (CKT) 496 for a voltage that is more than 0.64 volt and less than 3.1 volts.

^ If voltage is too high or too low for 5 seconds, Diagnostic Trouble Code (DTC) P0326 will set.
^ If a DTC P0326 is set refer to that Diagnostic Trouble Code Charts.

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. Determines 5 volts at each knock sensor and faulty knock sensor(s).
3. Determines wiring fault on CKT 496.
4. Checks continuity of circuit for grounded circuit and through process of elimination diagnoses VCM-A.

DIAGNOSTIC AIDS
The VCM-A applies 5 volts to CKT 496. The 8200 ohm resistor in each knock sensor together 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 VCM-A, 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 Detonation/Spark Knock. Detonation/Spark Knock/Pings

CAUTION: DO NOT backprobe VCM-A connectors as damage to seals may occur.