Does anyone know how to change the knock sensor on a 1998 subaru outback . or where i can get a diagram to see

A 98 Outback should be equipped with the EJ255 DOHC engine.. there may be one or two knock sensors.. depending on the build of the car. If you remove the airbox ( large black square thing on the rear of the engine, attaches to the throttle body), they should be visible under the intake manifold. Most models have one for each cylinder head, and they will be at opposite sides of the engine, screwed into the block itself with a one wire connector.