Circuit Description

WARNING: This page is about a different car, the 2002 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.

Fuel trim refers to feedback compensation value compared against basic injection time. Fuel trim includes short-term and long-term fuel trim.

DTC P0171 and DTC P0174 are set when fuel trim is driven rich beyond a certain value. Possible causes are:

Air intake (hose loose).
Fuel line pressure.
Injector blockage.
Open or short in A/F sensor circuit.
A/F sensor malfunction.
Airflow meter.
Engine coolant temperature sensor.
Gas leakage on exhaust system.
PCV hose connection.

DTC P0172 and DTC P0175 is set when fuel trim is driven lean beyond a certain value. Possible causes are:

Air induction system.
Fuel line pressure.
Injector blockage.
Open or short in A/F sensor circuit.
A/F sensor malfunction.
Airflow meter.
Engine coolant temperature sensor.
Gas leakage on exhaust system.
PCV hose connection.