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

Solution

1. Preparation

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

2. Inspect and Repair Air Intake System

• Sub-steps:
  • Visually check all air intake hoses for signs of wear or damage.
  • If any hoses are cracked or leaking, replace them with OEM parts.
  • Inspect the intake manifold gasket for leaks and replace if necessary.
• Tools Required: Socket set, screwdriver set
• Safety Warnings: Ensure the engine is off and cool.

3. Check and Clean MAF Sensor

• Sub-steps:
  • Locate the MAF sensor on the air intake duct.
  • Disconnect the electrical connector and remove the sensor using a socket.
  • Clean the sensor using MAF cleaner and let it dry completely before reinstalling.
• Tools Required: Torx screwdriver, MAF cleaner
• Safety Warnings: Avoid touching the sensor element with fingers to prevent damage.

4. Test Fuel Pressure

• Sub-steps:
  • Connect a fuel pressure gauge to the fuel rail test port.
  • Turn the ignition to the "On" position (do not start) to check the pressure reading.
  • Compare the reading with manufacturer specifications; if low, check the fuel pump and filter.
• Tools Required: Fuel pressure gauge
• Safety Warnings: Relieve fuel system pressure before connecting the gauge.

5. Inspect and Clean Fuel Injectors

• Sub-steps:
  • Remove the fuel rail to access the injectors (ensure fuel system pressure is relieved).
  • Inspect injectors for any signs of clogging; use a fuel injector cleaning kit if needed.
  • Reinstall the injectors and fuel rail, ensuring proper sealing and torque specifications are followed.
• Tools Required: Socket set, fuel injector cleaning kit
• Safety Warnings: Use caution when handling fuel components.