AIR Fuel Ratio

The scan tool range is 0.0 to 25.5. The air fuel ratio indicates the PCM commanded value. In a closed loop, the air fuel ratio should normally be around 14.2-14.7. A lower air fuel ratio indicates a richer commanded mixture, which may be seen during Power Enrichment or Three-way Catalytic Converter (TWC) Protection modes. A higher air fuel ratio indicates a leaner commanded mixture. This can be seen during Decel Fuel Mode.