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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative terminal of the battery to ensure safety.

2. Inspect and Repair Intake System

• Tools Required: Socket set, screwdrivers, vacuum gauge
• Sub-steps:
  1. Visually inspect the air intake ducts for any cracks or loose connections.
  2. Use a vacuum gauge to check for any vacuum leaks in the system.
  3. Tighten any loose clamps or replace any damaged hoses as needed.

3. Clean or Replace MAF Sensor

• Tools Required: MAF sensor cleaner, torque wrench
• Sub-steps:
  1. Disconnect the MAF sensor electrical connector.
  2. Remove the MAF sensor from the air intake housing using a socket set.
  3. Clean the MAF sensor with MAF sensor cleaner; do not touch the sensor element.
  4. Reinstall the sensor and reconnect the electrical connector, tightening to manufacturer torque specifications.

4. Check and Adjust Fuel System

• Tools Required: Fuel pressure gauge, fuel injector cleaner
• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail and turn the ignition on (do not start the engine) to check fuel pressure.
  2. If pressure is low, replace the fuel pump or fuel filter as necessary.
  3. If injectors are suspected to be clogged, use a fuel injector cleaner according to instructions to clean them.

5. Inspect Coolant Temperature Sensor

• Tools Required: Multimeter
• Sub-steps:
  1. Locate the engine coolant temperature sensor and disconnect the electrical connector.
  2. Use a multimeter to check the resistance of the sensor according to the manufacturer's specifications.
  3. Replace the sensor if it is outside the specified resistance range.