Error Code P0171
Moderate Issue
DTC Code P0171 indicates a Fuel Trim System Lean condition on Bank 1, where the Engine Control Module (ECM) detects a lean air/fuel mixture and adjusts the fuel delivery to compensate.
What symptoms indicate Error Code P0171?
- Engine Light ON: The check engine light or service engine soon warning light illuminates, indicating a potential issue with the fuel trim system on bank 1.
- Excessive Fuel Consumption: The vehicle may consume more fuel than usual, which can be linked to a lean condition in the fuel trim system on bank 1.
What causes OBD code Error Code P0171?
- The air filter may be dirty or restricted, causing insufficient airflow to the engine.
- A dirty or faulty Mass Air Flow (MAF) sensor can provide incorrect air intake readings.
- Intake air leaks can lead to unmetered air entering the engine, affecting the air-fuel mixture.
- Exhaust gas leaks before the oxygen sensor can skew sensor readings, leading to incorrect fuel trim adjustments.
- Fuel contamination can affect combustion efficiency, leading to a lean condition.
- Faulty or clogged fuel injectors may not deliver the correct amount of fuel.
- A faulty front heated oxygen sensor can provide inaccurate data to the engine control unit.
- Ignition misfiring can result in incomplete combustion, affecting the air-fuel ratio.
- Low fuel pressure can cause insufficient fuel delivery to the engine.
- Leaks in the Positive Crankcase Ventilation (PCV) hose can introduce unmetered air into the intake system.
How to fix OBD code Error Code P0171?
- Initial Inspection: Begin by checking for any additional DTCs, especially P0174, which may indicate an intake leak. Inspect the intake system for any visible leaks or damage.
- Check for Vacuum Leaks: Perform a thorough inspection for vacuum leaks in the intake manifold, hoses, and connections. Use a smoke machine if necessary to identify any hidden leaks.
- Inspect Air Filter: Examine the air filter for dirt or obstructions. Replace the air filter if it is dirty or clogged to ensure proper airflow.
- Clean Mass Air Flow (MAF) Sensor: Remove and clean the MAF sensor using a dedicated MAF cleaner. Ensure it is free of dirt and debris, then reinstall it securely.
- Test MAF Sensor: Use a multimeter to test the MAF sensor's voltage and signal output. Compare the readings to the manufacturer's specifications to determine if the sensor is functioning correctly.
- Inspect Front Heated Oxygen (O2) Sensor: Check the O2 sensor for proper operation. Use an OBD-II scanner to monitor the sensor's live data and ensure it is responding correctly to changes in air-fuel mixture.
- Final Verification: After addressing any identified issues, clear the DTCs and perform a test drive. Monitor the fuel trim readings and ensure the P0171 code does not return.