Circuit Description

PCM internal circuitry can identify if vehicle fuel system is capable of supplying enough fuel during heavy acceleration (power enrichment). PCM monitors voltage from HO2S during power enrichment. During closed loop, when power enrichment mode is requested (by heavy acceleration), PCM will provide more fuel to engine. Under these conditions, PCM should detect a rich condition (high HO2S voltage). If high HO2S voltage is not recognized at this time, DTC P1171 will set. A plugged fuel filter restricted fuel line, restricted in-tank fuel filter or faulty fuel pump can prevent enough fuel from being supplied during power enrichment mode.

When DTC sets, PCM will not illuminate MIL. PCM will store conditions present when DTC was set as FAILURE RECORDS data only. Information will not store as freeze frame data.

PCM will turn MIL off on third consecutive trip cycle during which diagnostic runs and fault is no longer recognized. A history DTC will clear after 40 consecutive trip cycles during which diagnostic runs and fault is no longer recognized. DTC can be cleared with scan tool, or by disconnecting battery voltage feed to PCM.