Knock Sensor: Removal

Disconnect the ground terminal from battery sensor. Ref. to BATTERY
Remove the bolt securing the connector to the A/C compressor.

Fig 1: Locating A/C Compressor Bolt
Courtesy of SUBARU OF AMERICA, INC.
Disconnect the connector (A) from the knock sensor, and remove the knock sensor from the cylinder block.

Fig 2: Locating Knock Sensor Connector And Bolt

Courtesy of SUBARU OF AMERICA, INC.