P0171, P0172, P0174, P0175

ADAPTIVE FUEL

Monitoring Procedure
If the fuel system is continually indicating an air/fuel ratio (AFR) closed loop compensation value fixed at the minimum value during steady driving, the purge valve is closed. If the value still remains at minimum, the fuel system is judged to have failed rich.

If the AFR closed loop compensation value stays above a value mapped against load and speed for too long, the fuel system is judged to have failed lean.

For both rich and lean diagnostics the relevant diagnostic trouble code (DTC) is stored if the failure judgement is made on two successive trips.

NOTE: The fuel system judgements are also used to perform the upstream Heated Oxygen Sensor (HO2S) sensor low voltage diagnostics.