how to fix P0171 code in Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Ensure the vehicle is on a flat surface and secured with wheel chocks.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Vacuum gauge, hose clamps, screwdriver
• Steps:
  1. Use a vacuum gauge to check for leaks in the intake manifold and hoses.
  2. Inspect all hoses and gaskets for signs of wear or cracks.
  3. Replace any damaged hoses or gaskets and secure them properly.

3. Clean the Mass Air Flow Sensor

• Tools Required: MAF cleaner, soft cloth
• Steps:
  1. Locate the MAF sensor in the air intake duct.
  2. Remove the electrical connector and unscrew the sensor from the duct.
  3. Spray the MAF cleaner onto the sensor's wire elements (do not touch them) and let it dry completely before reinstallation.

4. Test Fuel Pressure

• Tools Required: Fuel pressure gauge
• Steps:
  1. Connect the fuel pressure gauge to the fuel rail test port.
  2. Turn the ignition to the "ON" position without starting the engine and check the pressure reading.
  3. Compare the reading to the manufacturer’s specifications (usually found in the service manual).
  4. If the pressure is low, check the fuel pump and filter for issues, replacing as necessary.

5. Inspect and Clean Fuel Injectors

• Tools Required: Fuel injector cleaning kit
• Steps:
  1. Remove the fuel rail and injectors from the engine.
  2. Use a fuel injector cleaning kit to clean each injector thoroughly.
  3. Inspect all O-rings for wear and replace them if necessary before reinstallation.

6. Reassemble and Clear Codes

• Reinstall the intake components and reconnect the battery.
• Use the OBD-II scanner to clear the P0171 code and any other related codes.