Circuit Description

WARNING: This page is about a different car, the 2003 Toyota Tundra. However, it is still accessible from the selected car via links, so may be relevant.

The fuel trim is related to the feedback compensation value, not to the basic injection time. The fuel trim includes the short-term fuel trim and the long-term fuel trim. The short-term fuel trim is the short-term fuel compensation used to maintain the air-fuel ratio at its ideal theoretical value. The signal from the A/F sensor is approximately proportional to the existing air-fuel ratio. Comparing it with the ideal theoretical value, the ECM reduces fuel volume immediately if the air-fuel ratio is RICH and increases fuel volume if it is LEAN. The long-term fuel trim compensates for the deviation from the central value of the short-term fuel trim which is stored up by each engine tolerance, and the deviation from the central value due to the passage of time and changes of environment. If both the short-term fuel trim and long-term fuel trim exceed a certain value, it is detected as a malfunction and the MIL lights up.