my Toyota Highlander Third Generation (2014-2019) has an error code P0171 how to fix it

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down before working on it.

2. Inspect and Repair Air Intake System

• Tools Required: Socket set, screwdrivers, vacuum gauge
• Locate the air intake duct and visually inspect for cracks or loose connections.
• If any issues are found, replace the damaged sections of the duct or re-secure loose components.
• Use a vacuum gauge to check for leaks in the intake manifold; repair as needed.

3. Test and Clean MAF Sensor

• Tools Required: MAF sensor cleaner
• Disconnect the wiring harness from the MAF sensor.
• Remove the MAF sensor using the appropriate socket size.
• Spray the MAF sensor with MAF cleaner and let it dry completely before reinstallation.
• Reinstall the sensor and reconnect the wiring harness.

4. Check and Adjust Fuel Pressure

• Tools Required: Fuel pressure gauge
• Locate the fuel rail and connect the fuel pressure gauge.
• Turn the ignition to the ON position without starting the engine to check the fuel pressure.
• Compare the reading to the manufacturer's specifications (typically 40-60 psi for most vehicles).
• If the pressure is low, check the fuel pump and filter; replace if necessary.

5. Inspect Oxygen Sensors

• Tools Required: O2 sensor socket
• Locate the upstream oxygen sensor and disconnect the wiring harness.
• Remove the sensor using an O2 sensor socket.
• Inspect the sensor for damage; replace if necessary.
• Reinstall the new sensor and reconnect the wiring harness.

6. Test Fuel Injectors

• Tools Required: Fuel injector cleaning kit
• Remove the fuel rail with the injectors attached.
• Use the cleaning kit to clean the injectors or replace them if they are clogged or leaking.
• Reinstall the fuel rail and ensure all connections are secure.