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

Solution

1. Preparation

• Tools Required: OBD-II scanner, vacuum gauge, fuel pressure gauge, socket set, torque wrench, cleaning supplies, safety goggles, gloves.
• Disconnect the battery to ensure safety during repairs.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  • Use a vacuum gauge to check for leaks in the intake manifold.
  • Inspect all vacuum lines for cracks or disconnections.
  • Replace any damaged hoses or gaskets as necessary.

3. Clean the MAF Sensor

• Sub-steps:
  • Remove the MAF sensor from the intake duct.
  • Use a specialized MAF cleaner to spray the sensor elements. Avoid touching them.
  • Reinstall the MAF sensor after it is dry and clean.

4. Check and Adjust Fuel Pressure

• Sub-steps:
  • Connect the fuel pressure gauge to the fuel rail.
  • Turn the ignition to the "ON" position without starting the engine to check the pressure.
  • If the pressure is below specifications (usually around 50-60 psi for most Toyota engines), check the fuel pump and filter. Replace if necessary.

5. Inspect and Clean Fuel Injectors

• Sub-steps:
  • Remove the fuel injectors from the engine.
  • Use an injector cleaning kit to clean each injector or replace if they are clogged or leaking.
  • Reinstall the injectors with new O-rings to prevent leaks.

6. Clean the Throttle Body

• Sub-steps:
  • Remove the air intake duct to access the throttle body.
  • Use throttle body cleaner to clean the inside of the throttle body, removing any carbon buildup.
  • Reconnect the duct securely after cleaning.