ZQ8 Blazer

Bump. Still having this problem. I hear no audible knock, but when I create it manually (hit a wrench against the block) it doesn't show knock. I'm curious as to if it were working properly that I'd have a noticeable gain in power or not because currently I don't think it's making enough HP.

Suburbazine

You should take a multimeter and measure mV (millivolt) output on the sensor wire when you tap on the block near the sensor. Should see between 200 and 500ish mV per tap. If you're seeing it, the sensor is working. FYI- cheap multimeters do not read brief mV pulses well, or at all. Look at using a Fluke (readily available) or a DranTech (expensive, rare, super duper accurate) to test the sensor.

As I understand it, the PCM will not go into knock retard with a wrench in most circumstances because it times the noises to the firing order. If the noise is significantly off a combustion event the PCM discards it as ambient noise. It generally needs to happen more than once (multiple cylinders knocking) before retard kicks in.

If the PCM is not showing knock, you're not getting retard and it's probably not the source of your power issue (But something else in the timing could be). If you're not getting a low signal code then the sensor is probably signaling the PCM just fine. If you did have a low (or high) signal issue the PCM would have locked you into a maximum safety spark advance table and tossed a code.