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

Solution

1. Preparation

• Tools Required: OBD-II scanner, fuel pressure gauge, MAF sensor cleaner, torque wrench, socket set, vacuum gauge.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Repair Air Intake System

• Inspect all vacuum lines and the intake manifold for any signs of wear or damage.
• Replace any cracked or loose hoses.
• Reconnect all components and ensure there are no leaks.

3. Check and Clean MAF Sensor

• Locate the MAF sensor in the air intake duct.
• Disconnect the electrical connector and remove the sensor from the duct.
• Spray the MAF sensor with MAF cleaner and allow it to dry completely.
• Reinstall the sensor and reconnect the electrical connector.

4. Test Fuel Pressure

• Attach the fuel pressure gauge to the fuel rail test port.
• Start the engine and observe the fuel pressure; it should match the specifications outlined in the service manual (typically around 50-60 psi).
• If the pressure is low, replace the fuel pump or the fuel filter as needed.

5. Examine Fuel Injectors

• Inspect the fuel injectors for any signs of clogging or malfunction.
• If necessary, use a fuel injector cleaner or replace the injectors.

6. Check and Replace Oxygen Sensor

• If the oxygen sensor is faulty, locate the sensor (usually in the exhaust manifold) and disconnect the electrical connector.
• Remove the oxygen sensor using a socket wrench.
• Install the new oxygen sensor and reconnect the electrical connector.