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 ignition coil generates electrical signals which are transmitted to the ECU. The ECU calculates time between electrical pulses to determine engine speed. This information is used to control fuel delivery time, EGR, secondary air management and idle speed.