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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the vehicle's battery to ensure safety during repairs.

2. Inspect and Repair Air Intake System

• Sub-steps:
  • Inspect the air intake duct and connections for cracks or leaks; replace any damaged components.
  • Inspect all vacuum hoses for wear or leaks.
  • Tighten any loose clamps and connectors.

3. Check and Adjust Fuel Pressure

• Sub-steps:
  • Connect a fuel pressure gauge to the fuel rail.
  • Turn the ignition to the "on" position (without starting) to check the fuel pressure reading.
  • If the pressure is below specifications, replace the fuel pump or check the fuel filter for clogs.

4. Clean or Replace MAF Sensor

• Sub-steps:
  • Locate the MAF sensor in the air intake duct.
  • Remove the connector and unscrew the sensor from the duct.
  • Clean the sensor using MAF cleaner spray; if damaged, replace it with a new one.

5. Inspect and Clean Fuel Injectors

• Sub-steps:
  • Remove the fuel rail assembly to access the injectors.
  • Inspect each injector for clogs or leaks; clean them using a professional injector cleaning kit or replace if necessary.
  • Reinstall the fuel rail securely and ensure all connections are tight.

6. Check Oxygen Sensors

• Sub-steps:
  • Locate the upstream oxygen sensor and inspect the wiring for damage.
  • Use a multimeter to check the sensor's voltage output; if out of specification, replace the sensor.
  • Reconnect all components and ensure proper sealing.