Single Knock Sensor System

DTC 43 SINGLE KNOCK SENSOR SYSTEM
(PCM - Automatic Transmission)

DTC 43 Chart (Single Knock Sensor):

DTC 43 Circuit (Single Knock Sensor):

Circuit Description:
The DTC 43 circuit consists of a knock sensor with one wire that goes directly to the PCM. There are two DTC 43 checks performed by the PCM. One check consists of monitoring CKT 496 for a voltage that is more than 4.3 volts and less than .64 volt.

DTC 43 Will Set When: If voltage is either too high or too low, for 10 or more seconds, DTC 43 will set.

Action Taken (PCM will default to): The Malfunction Indicator Lamp (MIL) will illuminate.

DTC 43 Will Clear When: Conditions for fault are no longer present and Tech 1 "clear DTCs" function is used or 50 ignition switch keycycles have passed with no further faults or ignition switch is turned "OFF" and ECM B fuse is removed for 10 seconds.

DTC 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.

Diagnostic Aids: The PCM applies 5 volts to CKT 496. A 3.9k ohm resistor in the knock sensor 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 spark.

For further information, refer to DIAGNOSIS BY SYMPTOM/ INTERMITTENTS - Intermittent Malfunctions.