Code 43, Knock Sensor Circuit (Dual Sensors): Notes

Knock sensor informs PCM of engine detonation. PCM will retard ignition timing based on signals from knock sensors. Knock sensors produce an AC voltage signal which is proportional to amount of engine detonation (knock). Internal sensor circuitry causes 5-volt DC reference signal sent by PCM to be pulled low to about 1.5 volts. Any AC voltage produced by sensors will travel to PCM on this same reference line. Code 43 will set if: one sensor circuit becomes open, resulting in a 2.2 to 4.1-volt reference being monitored by PCM, both sensor circuits become open, resulting in a reference voltage greater than 4.1 volts being seen by PCM, or one or both circuits become grounded, resulting in a low (less than .78 volt) reference voltage being seen by PCM.

If an audible knock is heard from engine, repair internal engine problem, as normally no knock should be detected at idle. PCM supplies 5 volts on knock sensor circuit which should be present at knock sensor terminals when sensors are disconnected. If knock sensor circuit is shorted to voltage, Code 43 will set. With both sensors and PCM disconnected, no voltage should be present. An improperly installed sensor can prevent knock sensor from grounding to block.

1. If an audible knock is heard from engine, repair internal engine problem, as normally no knock should be detected at idle.
2. Determines if knock sensor is faulty or if module is faulty.
3. Sensor signal circuit shorted to voltage will set code. With sensor and PCM unplugged, no voltage should be present.
4. An improperly installed sensor can cause code to set.
5. If short to battery voltage is found, additional component damage may have occurred. If code resets after repairs, rerun chart to detect additional faults.