SHRT FT1 and FT 2 Average

The scan tool displays Percentage. This parameter indicates the average of the short term fuel trim cells. The short term fuel trim cells are rated (Weighted) for the amount of which they are used. For example, the PCM rates an idle cell higher than a wide open cell. If a fueling malfunction is occurs in the idle cell and the wide open cell, the idle cell would affect more than then the wide open cell. A negative value significantly below 0% indicates that the fuel system is rich and the PCM is reducing the fuel delivery (decreased injector pulse width). A positive value significantly greater than 0% indicates that a lean condition exists and the PCM is compensating by adding fuel (increased injector pulse width). When the average of the cells reach a predetermined high or low, a fuel trim DTC sets.