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The knock sensor is a passive device that has no effect on engine idle.
Passive sensors; send information back to the controller in terms of resistance/ohms.
The active sensor will send information back to the controller in terms of Milliamps, mA or Volts .
HVAC/R
Nothing. The knock sensor is a passive part that will not affect how the engine runs.
The knock sensor has no effect on idle. It has no effect at all unless it is triggered by detonation. It is a passive device.
PIR = passive infared They detect motion and then activate a switch to turn things on and off