| CAUTION | If ECM replacement is instructed in following testing, always ensure ECM connectors and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. |
Note. Oxygen sensor located in front of catalytic converter is referred to as sensor No. 1. Oxygen sensor located behind catalytic converter is referred to as sensor No. 2.
Circuit Description
Fuel trim refers to feedback compensation value compared against basic injection time. Fuel trim includes short-term and long-term fuel trim.
DTC P0171 is set when fuel trim is rich beyond a certain value. Possible causes are
- Air intake hose loose.
- Fuel line pressure.
- Injector blockage.
- Heated oxygen sensor.
- Mass Airflow (MAF) sensor.
- Engine Coolant Temperature (ECT) sensor.