how to fix P0171 code in my Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative terminal of the battery to prevent electrical shorts.
• Allow the engine to cool down before working on any components.

2. Inspect and Repair Air Intake System

• Sub-steps:
  • Visually inspect the air intake hoses for cracks or loose connections.
  • Replace any damaged hoses and ensure all connections are secure.

3. Clean or Replace MAF Sensor

• Sub-steps:
  • Disconnect the MAF sensor electrical connector.
  • Remove the MAF sensor from the air intake duct.
  • Use MAF sensor cleaner to clean the sensor elements gently.
  • Reinstall the MAF sensor and reconnect the electrical connector.

4. Check and Repair Fuel System

• Sub-steps:
  • Connect the fuel pressure gauge to the fuel rail.
  • Turn the ignition key to the "ON" position (without starting) to check the pressure.
  • If pressure is below specifications (typically 50-60 psi), inspect the fuel pump and fuel filter for issues.
  • Replace the fuel filter if clogged, and consider replacing the fuel pump if necessary.

5. Inspect and Replace Oxygen Sensor

• Sub-steps:
  • Locate the upstream oxygen sensor (usually near the exhaust manifold).
  • Disconnect the electrical connector and remove the sensor using an oxygen sensor socket.
  • Install the new oxygen sensor, ensuring proper torque (typically 30 ft-lbs).
  • Reconnect the electrical connector.