Knock Sensor: Removal

Disconnect the ground cable from battery.

Fig 1: Connecting/Disconnecting Battery Ground Terminal
Courtesy of SUBARU OF AMERICA, INC.
Remove the clip (A) from the air intake boot.
Loosen the clamp (B) connecting the air intake boot and air cleaner case (rear).
Loosen the clamp (C) which connects the air intake boot and throttle body.

Fig 2: Identifying Air Intake Boot Clip And Clamps
Courtesy of SUBARU OF AMERICA, INC.
Remove the air intake boot from the throttle body, and move it to the left side wheel apron.

Fig 3: Identifying Air Intake Boot And Throttle Body
Courtesy of SUBARU OF AMERICA, INC.
Disconnect the connector (A) from the knock sensor, and remove the knock sensor from the cylinder block.

Fig 4: Identifying Knock Sensor Connector
Courtesy of SUBARU OF AMERICA, INC.