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

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

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Transmission Position Sensor/Switch: Description and Operation

Park/Neutral Safety Switch:






The PARK/NEUTRAL (P/N) switch indicates to the ECM/PCM when the transmission is in park, neutral or drive. This information is used for Torque Converter Clutch (TCC), EGR, timing, canister purge and IAC valve information. Disconnecting the P/N switch could cause improper idle speed, cruise control, timing, or TCC operation.