How do you verify knock sensors working?

[Joe Bob]

Never really thought about this until recently.....do you have to read the DME with a scanner?

[911pcars]

I have verified this method on other vehicles, but not a Porsche. Should be valid.

1. Connect a timing light to the engine.
2. Start engine and increase idle speed sufficiently to observe spark advance
3. While monitoring the ignition timing, position a large drift punch on a substantial part of the engine block/crankcase (near the knock sensor), then strike with a large steel hammer
4. Observe the ignition timing retard to confirm knock sensor activity.

Sherwood