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

Solution

1. Preparation

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

Tools Required:

• OBD-II scanner
• Vacuum gauge
• Fuel pressure gauge
• Torque wrench
• Socket set
• Multimeter
• Screwdrivers

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses and connections for cracks or disconnections.
  2. Use a vacuum gauge to check for leaks; a reading below normal indicates a leak.
  3. Replace any damaged hoses or reattach loose connections.

3. Clean or Replace the MAF Sensor

• Sub-steps:
  1. Locate the MAF sensor in the air intake duct.
  2. Remove the MAF sensor using the appropriate socket.
  3. Clean the MAF sensor with MAF cleaner spray (do not touch the sensor element).
  4. If damaged, replace the MAF sensor with a new one.

4. Check and Adjust Fuel Pressure

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail.
  2. Turn the ignition to the "ON" position without starting the engine, and check the pressure.
  3. The pressure should be within manufacturer specifications (check service manual).
  4. If pressure is low, inspect the fuel pump, fuel filter, and fuel lines for issues, and replace components as necessary.

5. Inspect Fuel Injectors

• Sub-steps:
  1. Remove fuel injectors from the fuel rail.
  2. Check for clogs or leaks.
  3. Clean the injectors using an ultrasonic cleaner or replace them if necessary.
  4. Reinstall the injectors with the appropriate torque specifications.

6. Check ECT Sensor

• Sub-steps:
  1. Locate the ECT sensor on the engine.
  2. Disconnect the electrical connector and use a multimeter to test the resistance.
  3. Compare the readings to the specifications in the service manual; replace the sensor if out of range.