The knock sensor for my 2001 Subaru Outback grounds through the engine block. I've seen various advice about whether to put dielectric grease on the underside (where the grounding takes place). Some say 'no' - it will add resistance to the ground path, others say 'yes' - the resistance is negligible, and it will help prevent corrosion.
So my question is: is it recommended to put dieletric grease between the knock sensor and the engine block? And why?
For context: I replaced the knock sensor 1 week ago, and I used dieletric grease. Seemed fine at first (no CEL, no OBDII codes), then today the CEL came back on with code P0328.