how to fix the P0171 code in my Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Ensure the vehicle is on a flat surface and safely elevated if needed.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
  2. Use a smoke machine or carburetor cleaner to identify leaks while the engine is running.
  3. Replace any damaged hoses or reconnect loose hoses securely.

3. Clean or Replace the MAF Sensor

• Sub-steps:
  1. Locate the MAF sensor in the air intake duct.
  2. Disconnect the electrical connector and unscrew the MAF sensor from the duct.
  3. Clean the sensor with MAF sensor cleaner if it appears dirty or replace it if damaged.
  4. Reinstall the MAF sensor and reconnect the electrical connector.

4. Check Fuel System Components

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail.
  2. Turn the ignition key to the "ON" position but do not start the engine to check the fuel pressure reading.
  3. Compare the reading to the manufacturer’s specifications (usually around 50-60 psi for most vehicles).
  4. If the pressure is low, check the fuel filter and replace if necessary, then check the fuel pump operation.

5. Inspect Fuel Injectors

• Sub-steps:
  1. Remove the fuel rail to access the injectors.
  2. Check for clogs or leaks at the fuel injectors.
  3. Clean the injectors using an ultrasonic cleaner or replace them if they are faulty.
  4. Reinstall the fuel rail and ensure all connections are secure.