VCM (Manual Transmission)

DTC 43 KS (VCM):

KS Circuit (Typical):

Circuit Description:
The DTC 43 circuit consists of two knock sensors with one wire which is spliced together and goes directly to the VCM.
Once engine temperature reaches 88°C or more, but not over 1O1°C and MAP readings above 81 kPa with engine speed below 3200 RPM respectively, the VCM will perform a self check by advancing the timing incrementally while anticipating a knock signal. If no knock signal is received during two consecutive tests, DTC 43 will be 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. An improperly installed knock sensor can prevent the knock sensor from grounding to the block

Diagnostic Aids:
NOTE: Incorrect timing may set a false DTC 43. Check base timing. Refer to "Distributor Ignition".

The VCM applies 5 volts to CKT 496. An 8.2 + or - .5 ohm resistor in the knock sensors reduces the voltage to about 2.5 volts. When knock occurs, the knock sensors produce 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.

For further information, refer to "Intermittents". - Intermittent Malfunctions