Monitor Description

Under closed-loop fuel control, fuel injection volumes that deviate from those estimated by the ECM cause 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 values. Deviations from the ECM's estimated fuel injection volumes also affect 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 the malfunction thresholds, the ECM interprets this a fault in the fuel system and sets a DTC. Example:

The average fuel trim learning value is more than +35 % or less than -35 %, the ECM interprets this as a fuel system malfunction.

Fuel Compensation Amount

Malfunction Threshold of LEAN Condition

Malfunction Threshold of RICH Condition



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