DTC 43

DTC 43:

Knock Sensor Circuit:

Circuit Description:
The Knock Sensor (KS) is used to detect engine detonation. The PCM receives the knock sensor signal and will retard Ignition Control (IC) timing until knock is not detected.

The circuitry within the KS will drop approximately half of the 5 volts applied to the sensor on CKT 496. When engine detonation occurs, the sensor produces an A/C signal which rides on the 2.5 volt DC signal. The voltage amplitude and frequency is dependent upon the knock level emitted from the engine combustion process.

DTC 43 Will Set When:
The PCM detects above 4.6 volts or below .64 volt for 10 seconds.

Action Taken (PCM will default to):
The MIL will become illuminated. Knock retard will he fixed at 150 of timing retard.

DTC 43 Will Clear When:
A current DTC 43 will clear when the PCM senses the signal voltage level between .85 and 4.5 volts. A History DTC 43 will clear after 50 consecutive ignition key cycles without a current DTC being stored.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. If the conditions for DTC 43, as described above, are being met, the Tech 1 scan tool will always indicate "Yes" when the knock signal position is selected. If an audible knock is heard from the engine, repair the internal engine problem, as normally no knock should be detected at idle.

2. The PCM applies a 5 volt signal to the sensor on CKT 496.

3. This step determines if the knock sensor resistance is 3900 ohms +/- 15%. If the resistance is between 3300 to 4500 ohms, the sensor is OK.

Diagnostic Aids:
Check CKT 496 for an intermittent open or short to ground. Also, check for proper installation of KS module.

If the knock sensor CKT 496 is routed too close to secondary ignition wires, it may induce a voltage and cause a false knock signal.

See "Detonation/Spark Knock," in "Diagnosis By Symptom." Detonation/Spark Knock/Pings

If the customers complaint is the MIL (Check Engine) comes "ON" when in acceleration, the "B" portion of the DTC is failing. There is a possibility that the electronic ignition system was in bypass mode when the DTC 43 test was run. An intermittent open in the bypass which will not allow the spark to be advanced so the DTC 43 test would fail. If the PCM also had a DTC 42 stored, then the IC circuit is likely the cause of the DTC 43.