This may sound blindingly obvious, but if you've got a new det sensor telling you you've got det... maybe you're getting some det, and you need to sort that out.
What other symptoms have you got; have you changed anything recently? Is there any possibility that you are actually getting some detonation, or is there something that rattles/vibrates a little too much that could be fooling it by shaking the engine?
Obviously if you're absolutely sure that everything is sweet, then maybe you need to look at the wiring for the sensor.