In order to provide the best possible combination of drivability, fuel economy and emission control, the PCM uses a closed loop air/fuel metering system. The PCM monitors the HO2S signal voltage and adjusts fuel delivery based it in closed loop fuel control. Changes in fuel delivery will be indicated by the long-term and the short-term fuel trim values. The ideal fuel trim value is around 0%. The PCM will add fuel when the HO2S signal is indicating a lean condition. Additional fuel is indicated by fuel trim values that are above 0%. The PCM will reduce fuel when the HO2S signal is indicating a rich condition. Reduction in fuel is indicated by fuel trim values that are below 0%.
If long-term and short-term values are out of threshold value, the PCM determines that a fault exists and a DTC is stored.
Item | Detecting Condition | Possible cause | |
DTC Strategy | ● A/F learnt value (KLRN) & Integral value of A/F feedback compensation (KI) are monitored. | ● Poor connection ● Air leakage ● Improper fuel line pressure ● Faulty Injector ● Faulty Fuel Pump ● Faulty PCM | |
Enable Conditions | ● Closed loop | ||
Threshold value | ● A/F learnt value (KLRN) | LEAN | |
Integral value of A/F | ＞12.5% | ||
F/B compensation(Ki) | ＞7% | ||
Idle(KLRN + Ki) | ＞17% | ||
Diagnosis Time | ● continuous | ||
