do you have "lifetr tick" that doesn't go right away after startup? The knock sensor could be seeing that and reading it as knock or the sensor itself could be going bad. They tend to get really sensitive when they're on thier way out.
Dump in a 1/2 can of "RESTORE" a few hundred miles before your next oil change. Use the V-8 can. That got rid of my ticking AND my knock. My car was pulling timing because of my knock and it was just from my lifter tick.