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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Long Term FT-2

The scan tool display is counts. The PCM derives the Long Term Fuel Trim (FT) from the Short Term FT value. The Long Term FT represents a long-term correction in the fuel delivery. A value of 128 counts indicates that fuel delivery requires no compensation in order to maintain the desired air/fuel ratio. A value significantly less than 128 indicates that the fuel system is rich. When the fuel system is rich, the PCM reduces fuel delivery by decreasing injector pulse width. A value significantly greater than 128 indicates that a lean condition exists. During a lean condition the PCM increases fuel delivery by increasing injector pulse width. Fuel trim values at maximum authority may indicate an excessively rich or lean condition.