V70 XC AWD L5-2.4L Turbo VIN 56 B5254T (1998)
Knock Sensor: Description and Operation
KNOCK SENSORS
The function of the two Knock Sensors (KS) is to supply the ECM with the signals required to determine if the engine is knocking.
The ECM uses the KS and Camshaft Position (CMP) Sensor signals to identify the cylinder in which knock is present.
The engine management system incorporates two KS, each of which consists of the following components:
^
Housing (1)
^
Sleeve (2)
^
Piezoelectric crystal (3)
^
Contact strips (4)
^
Damping weight (5)
^
Washer (6)
^
Nut (7)
Engine knock produces vibrations which are transmitted through the block. The piezoelectric crystal (3) reacts to these by transmitting a signal, which
is a function of the frequency and amplitude of the sound waves, to the ECM.
The front KS detects knock in cylinders 1, 2 and 3, while the rear KS serves cylinders 4 and 5.
The sensors are mounted on the cylinder block.
