Yes I was a little crappy, seemed the point was being missed and over analyzed.
The device is a coil that generates a low voltage when certain frequencies are 'heard' or rather 'felt' through direct contact with the block. (A frequency, or range of frequencies, corresponding to detonation in the engine). The low voltage signal is sent to the ECU which retards the timing to prevent further detonation.
It's in a less than ideal environment, cycles of hot and cold, petroleum products, vibration and dissimilar metal corrosion all work on it. The phenolic covering becomes embrittled and cracks allowing outside air, moisture etc to cause it to rust and fail.
I had a code for it, and when I removed my old one there were pieces from the cover missing and the coil inside was rusted. I removed another from a junk engine lying around and although it was cracked the computer is satisfied with it and the CEL has gone out.
Before I installed it to the engine, I hit on the idea of cleaning the outside with a dry rag and painting the casing with two coats of liquid electrical tape.
The small existing cracks were filled by the 'tape' and there is now a continuous flexible water tight, and petroleum resistant coating on it. Perhaps, I will never change it again, perhaps it will fail tomorrow.
Since it is fairly easy to get to, and since they all seem to be prone to failure, maybe it would make sense remove it and seal it with a flexible covering before it does fail, hence 'preventative' fix.
Yes, I apologize for being crappy, but you have to admit the line about the lawyer proofing the post is somewhat humorous. Reagrds.