Short Term FT Bank 1 and Bank 2

The scan tool displays - 11 to +20 percent. Short-term FT represents a short-term correction to fuel delivery by the PCM. This correction is in response to the amount of time the fuel control O2S voltage spends above or below the 450 mV threshold. If the O2S voltage has remained less than 450 mV, indicating a lean air/fuel mixture, the short-term FT will increase into the positive range above 0 percent, and the PCM will add fuel. If the O2S voltage stays above the threshold, short-term FT will decrease below 0 percent into the negative range while the PCM reduces fuel delivery to compensate for the indicated rich condition. Under certain conditions such as extended idle and high ambient temperatures, canister purge may cause short-term FT to read in the negative range during normal operation. The maximum authority of the PCM to control FT allows a range between - 11 to +20 percent. Fuel trim values at maximum authority may indicate an excessively rich or lean system.