what causes the P0171 code in Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Ensure the vehicle is parked on a flat surface.
• Disconnect the negative battery terminal to ensure safety.

2. Inspect and Repair Air Intake System

• Tools Required: Screwdrivers, pliers, flashlight.
• Sub-steps:
  1. Visually inspect the entire air intake system for cracks or loose connections.
  2. Tighten any loose clamps or connections.
  3. Replace any damaged hoses or components as necessary.

3. Clean and Test the Mass Air Flow (MAF) Sensor

• Tools Required: MAF sensor cleaner or electrical cleaner.
• Sub-steps:
  1. Remove the MAF sensor from the air intake duct.
  2. Spray the MAF sensor with the cleaner, allowing it to dry completely.
  3. Reinstall the MAF sensor and ensure it is securely connected.

4. Check Fuel System

• Tools Required: Fuel pressure gauge.
• Sub-steps:
  1. Connect the fuel pressure gauge to the fuel rail.
  2. Turn the ignition to the "ON" position without starting the engine and check the fuel pressure.
  3. If the pressure is low, inspect the fuel pump and filter for issues and replace if necessary.

5. Inspect Oxygen Sensors

• Tools Required: Multimeter.
• Sub-steps:
  1. Locate the upstream oxygen sensor on the exhaust manifold.
  2. Disconnect the sensor and use a multimeter to check the voltage output (it should fluctuate between 0.1V to 0.9V).
  3. Replace the oxygen sensor if it is not functioning properly.

6. Final Steps

• Reconnect the negative battery terminal.
• Clear the codes using the OBD-II scanner and test drive the vehicle.