Oh, so the voltage being displayed is via a cheap volt meter wired in?
my suggestion, and I could be wrong and don't want to offend you, is that may be wired into the wrong pins. Don't take that as a negative or having a go, sometimes going back to the start / basics is what has to happen. The whole 2.4 volts thing has confused everyone except you, because you have seen it and did it. Everyone else's knowledge of a knock sensor doesn't match your experience, and that is why you are getting a bit cranky..
But a knock sensor is a simple thing, understood by many, that doesn't put out a voltage. So something is up, which has impacted this thread in a big way. Can you confirm what pins you connected to?
Also, proper terms seriously matter, you can't just use different terminology that may be conflicting or not make sense then tell people to just accept it and move on.