Monitor Description
Under closed-loop fuel control, a fuel injection volume that deviates from that estimated by the ECM causes changes in the long-term fuel trim compensation value. The long-term fuel trim is adjusted when there are persistent deviations in the short-term fuel trim value. Deviations from the ECM's estimated fuel injection volume also affects the average fuel trim learning value, which is a combination of the average short-term fuel trim (fuel feedback compensation value) and the average long-term fuel trim (learning value of the air- fuel ratio). If the average fuel trim learning value exceeds a malfunction threshold, the ECM interpret this a fault in the fuel system and sets a DTC.
Example:
If the average fuel trim learning value is more than +35% or less than -35%, the ECM interprets this as a fuel system malfunction.