Long Term FT

Scan tool range is -23 to +16 percent. Long term fuel trim is derived from the short term fuel trim value and represents a long term correction of fuel delivery. A value of 0 percent indicates that fuel delivery requires no compensation to maintain the PCM commanded air/fuel ratio. A negative value significantly below 0 percent indicates that the fuel system is rich and fuel deliver is being reduced. A positive value significantly more than 0 percent indicates that a lean condition exists and the PCM is compensating by adding fuel.