What is the Normal Range for Long-Term Fuel Trim?

[LaDakota]

Long-term fuel trim normally ranges from -23% to 16%. Long-Term Fuel Trim: Long-term trim refers to normal aging issues such as component clearance during usage. A value of 0% indicates that no fuel compensation is required to maintain the PCM-commanded air-fuel ratio. Long-Term Trim Range: If significantly below 0% (a negative value), it indicates a rich system condition, and fuel delivery should be reduced (by decreasing injector pulse width). If significantly above 0% (a positive value), it indicates a lean condition, and the PCM will increase fuel delivery (by increasing injector pulse width) for compensation. Since long-term fuel trim tends to follow short-term fuel trim, negative values caused by idle purge valve operation are not considered abnormal. The PCM controls long-term fuel trim within the maximum allowable range of -23% to 16%, where these extreme values indicate either an excessively rich or lean system condition.