Code 52, Knock Sensor Signal Open Or Shorted Circuit VIN 5): Notes

The knock sensor is used to detect engine detonation. The ECM will retard the electronic spark timing based on signal being received. The knock sensor sends an AC voltage signal to the ECM through the Black wire and should measure about 2-300 mV AC. The amplitude and signal frequency are dependent upon the knock level.

If the Black wire becomes open or shorted to ground, voltage will drop to less than 200 mV. If this condition is met for about 5 seconds, Code 52 will be stored.

1. Code 52 will set when the following conditions are met for 5 seconds.
   • Coolant temperature is above 194°F (90°C).
   • MAT temperature is above 32°F (0°C).
   • There is high engine load based on MAF and RPM sensors.
   • Voltage on Black wire is less than 200 mV.

Repair internal engine problem if knock is detected at idle.

1. If tapping on engine lift hook does not produce a knock signal, try tapping closer to sensor before proceeding.
2. This checks the resistance of the knock sensor.