how to fix P0171 code in Toyota Corolla E170 (2013-2019)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool down before starting.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  • Visually inspect all vacuum hoses and connections for signs of wear, cracks, or disconnections.
  • Use a smoke machine or carburetor cleaner around the intake manifold and vacuum lines. Listen for hissing sounds or observe any change in engine RPM.
  • Replace any damaged hoses or seals.
• Tools Required: Vacuum hose kit, smoke machine (optional), carburetor cleaner.

3. Check and Clean the MAF Sensor

• Sub-steps:
  • Locate the MAF sensor in the air intake duct.
  • Disconnect the electrical connector from the MAF sensor.
  • Remove the MAF sensor using the appropriate socket.
  • Clean the MAF sensor using MAF cleaner spray; do not touch the sensing element.
  • Reinstall the MAF sensor and reconnect the electrical connector.
• Tools Required: Torque wrench, socket set, MAF cleaner spray.

4. Test Fuel Pressure

• Sub-steps:
  • Connect the fuel pressure gauge to the fuel rail service port.
  • Turn the ignition to the ON position (do not start) and check the fuel pressure reading against manufacturer specifications (typically 43-50 psi for Corolla).
  • If pressure is low, inspect the fuel pump and fuel filter for blockage or failure.
• Tools Required: Fuel pressure gauge.

5. Repair or Replace Oxygen Sensors

• Sub-steps:
  • Use an O2 sensor socket to remove the upstream (pre-catalytic converter) oxygen sensor.
  • Inspect the old sensor for any signs of damage or contamination.
  • Install the new oxygen sensor and torque to manufacturer specifications (usually around 30 lb-ft).
• Tools Required: O2 sensor socket, torque wrench.