how to resolve P0171 code in my Toyota Highlander Fourth Generation (2020-present)?

Solution

1. Preparation

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

2. Inspect and Repair Air Intake System

• Tools Required: Vacuum gauge, hose clamps, screwdriver, torque wrench
• Instructions:
  1. Visually inspect all vacuum hoses for cracks or disconnections.
  2. Use a vacuum gauge to check for vacuum leaks; if any are found, replace the affected hoses.
  3. Ensure that the air intake duct is securely attached and there are no leaks.

3. Clean or Replace MAF Sensor

• Tools Required: MAF sensor cleaner, screwdriver
• Instructions:
  1. Locate the MAF sensor in the air intake system.
  2. Disconnect the electrical connector and remove the sensor.
  3. Spray MAF sensor cleaner on the sensor element; do not touch it with fingers or tools.
  4. Reinstall the sensor after it has dried, ensuring a secure fit.

4. Check Fuel System

• Tools Required: Fuel pressure gauge, multimeter
• Instructions:
  1. Connect a fuel pressure gauge to the fuel rail.
  2. Turn the ignition to the "ON" position (do not start) and check the pressure; it should match the manufacturer’s specifications.
  3. If pressure is low, inspect the fuel pump, filter, and lines for issues. Replace any faulty components.
  4. If injectors are suspected, remove and clean or replace them as necessary.

5. Test and Replace Oxygen Sensors if Necessary

• Tools Required: Multimeter or OBD-II scanner
• Instructions:
  1. Use a multimeter to check the voltage output of the oxygen sensors; they should fluctuate between 0.1V and 0.9V when the engine is running.
  2. If a sensor is reading consistently high or low, it may need to be replaced. Disconnect the battery and replace the faulty sensor.