Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

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Knock Sensor: Description and Operation


Knock Sensor:







The Knock Sensor is an electro-mechanical device capable of measuring vibration and converting it into an electrical signal. During engine knock, a variation in pressure on the sensor body produces current, which is transmitted to the Electronic Control Unit (ECU) through a cable consisting of two shielded wires.