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

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

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Engine Speed Sensor: Description and Operation

The engine speed signal is obtained from the ignition coil. Electric signals are sent to the ECU where the time between these pulses is used to calculate engine speed, controlling fuel delivery, secondary air management, deceleration spark and throttle opener operation.