Code 52, Knock Sensor Signal/Open Or Short CKT

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

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 greater than 32°F (0°C).
   • There is high engine load based on MAF and RPM.
   • Voltage on Black wire is less than 200 mV.

   Repair internal engine problem if knock is detected at idle.

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