you are correct but the knock sensor is not sensing vibrations. When knock occures the sensor picks up on a harmonic frequency within the block. If the sensor operated on vibrations then the ECU would have false readings during daily operation. Even piston slap would set the knock sensor off.

The only way to test would be to either send a simulated signal to the MS or to tune really lean and knock the motor. if your on factory ignition then you will know when you knock!

My snap on scanner reads the knock sensor in terms of voltage, not sure if the MS will read the same way or if the factory ecu reads in the same manner. I havent had a chance to really look into how the factory sensor signal operates.

Terry