Segun el manual

The ECM utilises active knock control, which serves to
prevent engine damage through pre-ignition or
detonation. Knock control is effective under all
operating conditions, enabling the engine to operate
without additional safety margins.

Two knock sensors are used, one mounted each side
of the cylinder block between the two centre cylinders
of each bank. Each sensor has two wires; a signal
wire providing input to the ECM and a ground
(screen). Each of the sensors monitor the ’knock’ from
four cylinders (Cylinder No’s: 1, 3, 5 & 7 and Cylinder
No’s: 2, 4, 6 & 8 ).

Fin del "copia y pega" disculpa el idioma, pero no sera dificil traducirlo

  Uno a cada lado del bloque, más o menos en el centro en el sentido longitudinal del bloque.

Se ven por abajo del motor?

Enviado desde mi Redmi Note 3 Pro

  Pues creo recordar que si pero me parece que van bastante escondidos.