Long FT1 and 2 Average

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