Where is the knock sensor in a 1990 Chevy Pick up 4.3?

The knock sensor on a 1990 Chevy pickup with the 4.3L V6 engine is located on the passenger side of the engine block, near the front of the engine, and usually relatively low down. It's often near the oil filter or oil pan area.

However, the exact location can vary slightly depending on the specific engine configuration. It's best to consult a repair manual specific to your 1990 Chevy 4.3L pickup truck for a diagram and precise location. A picture in a repair manual or online forums showing that specific engine will be your best bet for pinpointing it.