DTC P0171 Or DTC P0172: Condition

DTC P0171 is set when Engine Control Module (ECM) detects that total fuel trim is more than 33 percent. DTC P0172 is set when ECM detects that total fuel trim is less than -33 percent. MIL is illuminated when ECM detects either malfunction during 2 consecutive drive cycles. Possible causes are:

• ECM malfunction.
• Engine Coolant Temperature (ECT) sensor.
• Exhaust Gas Recirculation (EGR) system malfunction.
• Exhaust system leaks.
• Fuel level sensor malfunction.
• Heated Oxygen Sensor No. 1 (HO2S-1) malfunction.
• Incorrect fuel pressure.
• Mass Air Flow (MAF) sensor malfunction.
• Vacuum leaks.