Circuit Description

Fuel trim refers to feedback compensation value compared against basic injection time. Fuel trim includes short-term and long-term fuel trim. If total of short term fuel trim value and long term value is within 35 percent, system is functioning properly. DTC P0171/P0174 is set when fuel trim command is rich beyond a certain value. Possible causes are:

• Air intake system leak.
• Injector blockage.
• Faulty Mass Airflow (MAF) sensor.
• Faulty Engine Coolant Temperature (ECT) sensor.
• Fuel line pressure.
• Exhaust system leak.
• Open or short in A/F sensor circuit (Banks No. 1 or 2, Sensor No. 1).
• Faulty A/F sensor (Banks No. 1 or 2, Sensor No. 1).
• Faulty ECM.

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

• Injector blockage or leak.
• Faulty Mass Airflow (MAF) sensor.
• Engine Coolant Temperature (ECT) sensor.
• Ignition system malfunction.
• Fuel line pressure.
• Exhaust system leak.
• Open or short in A/F sensor circuit (Banks No. 1 or 2, Sensor No. 1).
• Faulty A/F sensor (Banks No. 1 or 2, Sensor No. 1).
• Faulty ECM.