Short Term FT

The Short Term FT represents a short term correction to fuel delivery by PCM/ECM in response to amount of time oxygen sensor voltage spends above or below 450 mv threshold. If oxygen sensor has mainly been below 450 mv, indicating a lean air/fuel mixture, short term fuel trim will increase to tell PCM/ECM to add fuel. If oxygen sensor voltage stays mainly above threshold, PCM/ECM will reduce fuel delivery to compensate for indicated rich condition.