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 threshold, the ECM interprets this a fault in the fuel system and sets a DTC.
Example:
The average fuel trim learning value is +35 % or more or -35 % or less, the ECM interprets this as a fuel system malfunction.
| Related DTCs | P0171: Fuel trim lean P0172: Fuel trim rich |
|---|---|
| Required Sensors/Components (Main) | Fuel system |
| Required Sensors/Components (Related) | A/F sensor, Mass air flow meter, Crankshaft position sensor |
| Frequency of Operation | Continuous |
| Duration | Within 10 seconds |
| MIL Operation | 2 driving cycles |
| Sequence of Operation | None |