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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Repair Air Intake System

• Check all hoses and connections from the air filter to the throttle body.
• Tools Required: Socket set, pliers
• Sub-steps:
  1. Remove the air intake duct and inspect for cracks or holes.
  2. Replace any damaged hoses or components.

3. Check for Vacuum Leaks

• Perform a visual inspection and smoke test for vacuum leaks.
• Tools Required: Smoke machine
• Sub-steps:
  1. Connect the smoke machine to the intake manifold.
  2. Observe for any smoke escaping, indicating a leak.
  3. Repair or replace any faulty hoses or gaskets.

4. Test Fuel Pressure

• Ensure the fuel system is delivering the correct pressure.
• Tools Required: Fuel pressure gauge
• Sub-steps:
  1. Locate the fuel pressure test port on the fuel rail.
  2. Connect the fuel pressure gauge and turn the ignition to the "ON" position without starting the engine.
  3. Check the reading; it should be within manufacturer specifications (usually around 50-60 psi).
  4. If low, investigate the fuel pump and filter.

5. Inspect and Clean MAF Sensor

• Ensure the MAF sensor is functioning correctly to avoid incorrect readings.
• Tools Required: MAF sensor cleaner, screwdriver
• Sub-steps:
  1. Disconnect the MAF sensor electrical connector.
  2. Remove the MAF sensor from the intake.
  3. Spray the MAF sensor cleaner onto the sensor element and let it dry completely before reinstallation.

6. Check Fuel Injectors

• Ensure fuel injectors are delivering the correct amount of fuel.
• Tools Required: Injector cleaning kit or replacement injectors
• Sub-steps:
  1. If injectors are clogged, use a cleaning kit to clean them.
  2. If they are faulty, replace with new injectors.