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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Ensure the engine is cool before starting work on the intake system.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Vacuum gauge, hose clamps, socket set
• Check all vacuum lines for cracks or disconnections.
• If a leak is found, replace the damaged hose or reattach the disconnected line.
• Use a vacuum gauge to confirm the system is sealed correctly.

3. Clean the Mass Air Flow (MAF) Sensor

• Tools Required: MAF cleaner or electronic cleaner, soft cloth
• Remove the MAF sensor from the air intake duct.
• Spray the MAF cleaner onto the sensing element of the sensor and let it dry completely.
• Reinstall the MAF sensor and ensure it's secured properly.

4. Check and Adjust Fuel Pressure

• Tools Required: Fuel pressure gauge, wrenches
• Connect the fuel pressure gauge to the fuel rail.
• Turn the ignition to the "ON" position (do not start) and check the pressure reading against the manufacturer's specifications.
• If the pressure is low, inspect the fuel filter and fuel pump for issues. Replace if necessary.

5. Inspect and Test Fuel Injectors

• Tools Required: Digital multimeter, injector cleaning kit (if needed)
• Check for proper electrical connection to the fuel injectors using a multimeter.
• Perform a fuel injector balance test to ensure all injectors are delivering fuel properly.
• Clean or replace any malfunctioning injectors as needed.