Circuit Description
WARNING: This page is about a different car, the 2003 Toyota 4Runner. 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.
DTCs P0171 and/or P0174 is set when fuel trim is considerably in error on LEAN side, beyond a certain value with engine at normal operating temperature and the actual air/fuel ratio is lean, (2-trip detection logic). 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.
- Heated Oxygen Sensor (HO2S) circuit is open or shorted, (Bank 1 & 2, Sensor 1).
- Defective HO2S (Bank 1 & 2, Sensor 1).
- Defective HO2S heater (Bank 1 & 2, Sensor 1).
- Defective Positive Crankcase Ventilation (PCV) valve hose or connection.
- Defective ECM.
- Vehicle ran out of fuel.
DTCs P0172 and/or P0175 is set when fuel trim is considerably in error on RICH side, beyond a certain value with engine at normal operating temperature and the actual air/fuel ratio is rich (2-trip detection logic). 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.
- HO2S circuit is open or shorted (Bank 1 & 2, Sensor 1).
- Defective HO2S (Bank 1 & 2, Sensor 1).
- Defective ECM.
- Vehicle ran out of fuel.