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.
• Improper fuel line pressure.
• Fuel injector restricted.
• Faulty heated oxygen sensor (bank No. 1 or 2, sensor No. 1).
• Faulty Mass Airflow (MAF) meter.
• Faulty Engine Coolant Temperature (ECT) sensor.
• Exhaust system leak.

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

• Improper fuel line pressure.
• Fuel injector restricted or leaking.
• Faulty heated oxygen sensor (bank No. 1 or 2, sensor No. 1).
• Faulty Mass Airflow (MAF) meter.
• Faulty Engine Coolant Temperature (ECT) sensor.
• Exhaust system leak.