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


The knock sensor is located on the engine block where detonation in each cylinder can be detected. This sensor provides information used by the SBEC to modify spark advance in order to eliminate detonation.