Monitor Description
Under closed-loop fuel control, fuel injection amounts that deviate from the ECM's estimated fuel amount will cause a change in the long-term fuel trim compensation value. Long-term fuel trim value is adjusted when persistent deviations in the short-term fuel trim's value are present. Also, the smoothed fuel trim learning value is adjusted when deviations from the ECM's simulated fuel injection value are present. The smoothed fuel trim learning value is the combination of smoothed short-term fuel trim (fuel feedback compensation value) and smoothed long-term fuel trim (learning value of the air fuel ratio). When the smoothed fuel trim learning value exceeds the malfunction threshold, the ECM interprets this as 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.