DTC P0171 Or DTC P0172: Condition

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

• ECM malfunction.
• Exhaust system leaks.
• Fuel injector malfunction.
• Fuel level sensor malfunction.
• HO2S-1 malfunction.
• Incorrect fuel pressure.
• Mass Air Flow (MAF) sensor malfunction.
• Vacuum leaks.