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 or P0174 is set when fuel trim is rich beyond a certain value. Possible causes are:

• Air induction malfunction.
• Injector leak/blockage.
• Faulty Mass Airflow (MAF) sensor.
• Faulty Engine Coolant Temperature (ECT) sensor.
• Fuel line pressure.
• Exhaust system leak.
• Open or short circuit in A/F sensor circuit (Bank 1 or 2 sensor 1)
• Faulty A/F sensor.
• Faulty ECM.

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

• Injector blockage or leak.
• Faulty Mass Airflow (MAF) sensor.
• Faulty Engine Coolant Temperature (ECT) sensor.
• Faulty ignition system.
• Fuel line pressure.
• Exhaust system leak.
• Open or short circuit in A/F sensor circuit (Bank 1 or 2 sensor 1)
• Faulty A/F sensor.
• Faulty ECM.