DTC P1171: Fuel System Lean During Acceleration: Description
WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
ECM can determine if engine is running rich when vehicle operator demands heavy acceleration. When heavy acceleration is demanded, ECM will go into power enrichment mode. During this mode, a lower air/fuel ratio than 14.7:1 (around 12.0:1) will be commanded and fuel injector pulse width will increase. During this condition, ECM should detect HO2S1 signal voltage go high and remain there. DTC sets when ECM is in power enrichment mode and HO2S1 signal voltage is too low.