2000 Accord knock sensor troubleshooting
 

I'm trying to test the knock sensor on a 2000 Accord 4 cylinder. The
Haynes service manual procedure involves draining the engine oil
removing the sensor and measuring the AC voltage generated by the
sensor by lightly tapping it with a hammer. This sensor is basically a
microphone. Why would it have to be removed from the engine block to
perform this test ? I would think that tapping the block where its
mounted should generate a reasonable test signal.