Short Term FT-2

The scan tool display is counts. The Short Term Fuel Trim (FT) represents a short term correction to the PCM controlled fuel delivery. The Short Term FT correction is driven by the fuel control oxygen sensor. When the oxygen sensor voltage remains below 450 mV the PCM adds fuel and the Short Term FT parameter is greater than 128. When the oxygen sensor voltage stays above 450 mV the PCM subtracts fuel and the Short Term FT parameter is less than 128. During an extended idle with high ambient temperatures, the EVAP canister may purge, causing the Short Term FT to read less than 128. This is a normal condition. The fuel trim values at maximum authority may indicate an excessively rich or lean condition.