Dual Knock Sensors VCM (Manual Transmission)

Knock Sensor (KS) Check Chart (VCM):

Knock Sensor (KS) Circuit (VCM):

Circuit Description:
The DTC 43 circuit consists of two knock sensors with one wire that goes directly to the VCM. There are two DTC 43 checks performed by the VCM. One check consists of monitoring CKT 496 for a voltage that is more than .04 volt and less than 4.6 volts.

If voltage is either too high or too low for 16 or more seconds, DTC 43 will set. Once engine temperature reaches 85°C, MAP is over 81 kPa, and engine speed is less than 3200 RPM, the VCM will perform a self check. This self check will advance the timing until it receives a knock signal. If no knock signal is received, DTC 43 will set.

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 knock sensor ground, or faulty sensor.

Diagnostic Aids:
The VCM applies 5 volts to CKT 496. A 8900 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 VCM, 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" in "Diagnosis By Sympton". Symptom Related Diagnostic Procedures