[amidgeha]

System Too Rich at Higher Load

In order to provide the best possible combination of driveability, fuel economy and emission control, the Powertrain Control Module (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%. The DTC relevant to fuel trim will be set when the amount reaches excessive levels because of a lean or rich condition.

Cause:
Leaking fuel injector or pressure regulator
High fuel pressure condition
Faulty front HO2S
Leak in exhaust system
Faulty Mass Air Flow (MAF) sensor

Symptoms:
Check engine light