Circuit Description
WARNING: This page is about a different car, the 2002 Lexus LX 470. 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 P0174 set when fuel trim is rich beyond a certain value. Possible causes are:
- Air induction system malfunction.
- Fuel injector restricted.
- Defective Mass Airflow (MAF) meter.
- Defective Engine Coolant Temperature (ECT) sensor.
- Improper fuel pressure.
- Exhaust system leak.
- Open or short in heated oxygen sensor circuit (bank No. 1 or 2, sensor No. 1).
- Defective heated oxygen sensor (bank No. 1 or 2, sensor No. 1).
- Faulty ECM.
DTC P0172 and P0175 set when fuel trim is lean beyond a certain value. Possible causes are:
- Fuel injector restricted or leaking.
- Defective Mass Airflow (MAF) meter.
- Defective Engine Coolant Temperature (ECT) sensor.
- Ignition system malfunction.
- Improper fuel pressure.
- Exhaust system leak.
- Open or short in heated oxygen sensor circuit (bank No. 1 or 2, sensor No. 1).
- Defective heated oxygen sensor (bank No. 1 or 2, sensor No. 1).
- Faulty ECM.