Looking at the top of the motor remove the air intake and it is below the butterfly on the drivers side top end of the motor.
It is located on the engine block drivers side.
that the knock sensor does
That depends entirely on what happened to it to make it need repairing.
the knock sensor in on the drivers side of the block toward the rear, and it's under the intake manifold.
Its on top of the engine by the fuel injection (remove the air intake first). Need a 10mm socket with a long extention.
In a 1998 Subaru Legacy, the knock sensor is located on the top of the engine block and to the left of the engine. More specifically, it is under the left rear intake manifold runner.
on top of the engine under the air box
You can find the knock sensor on the top side of the engine under the intake manifold. It is easiest to find from the driver's side and is at the back of the engine block.
It is threaded into the block, under the intake manifold.
Where is the knock sensor located on a 1999 Subaru Forester?
It is underneath the intake manifold. If you look straight down from your throttle body, you will see a sensor with one wire coming out and a bolt going through the middle of it, that is the knock sensor.
If somebody knocks on the front door of the Subaru, the KNOCK sensor, sets off the KNOCK Alarm....LOL