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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety during repairs.
• Allow the engine to cool down if it has been running.

2. Inspect and Repair Air Intake System

• Sub-steps:
  1. Visually inspect the air intake duct, including hoses and clamps, for any signs of wear, cracks, or disconnections.
  2. If damage is found, replace the damaged component (e.g., air duct or hose).
  3. Reconnect any loose connections securely.

3. Clean or Replace MAF Sensor

• Tools Required: MAF sensor cleaner or rubbing alcohol, soft cloth
• Sub-steps:
  1. Locate the MAF sensor in the air intake pathway.
  2. Disconnect the electrical connector from the MAF sensor.
  3. Remove the MAF sensor from its housing using a Torx or socket wrench.
  4. Clean the sensor element carefully with MAF cleaner; do not touch the sensor directly.
  5. Reinstall the MAF sensor and reconnect the electrical connector.

4. Check Fuel System

• Sub-steps:
  1. Use a fuel pressure gauge to check the fuel pressure at the fuel rail; compare the value with the manufacturer’s specifications.
  2. If pressure is low, inspect the fuel pump and fuel filter, replacing them if necessary.
  3. Ensure the fuel lines are free from leaks and properly connected.

5. Inspect Vacuum Lines and Intake Manifold

• Sub-steps:
  1. Visually inspect all vacuum lines connected to the intake manifold for cracks or disconnections.
  2. If any vacuum line is damaged, replace it.
  3. Check the intake manifold for cracks; if found, it may need to be replaced or repaired.