What does long term fuel trim mean?

Long term fuel trim (LTFT) refers to the adjustments the engine control unit (ECU) makes over time to the fuel mixture based on the engine's performance and sensor feedback. It helps optimize the air-fuel ratio for efficient combustion, emissions control, and engine performance. LTFT values indicate how much the ECU is altering the base fuel injection settings to compensate for factors like changes in air density, fuel variations, or engine wear. A significant deviation from the expected range can signal potential issues with the engine or fuel system.