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

Solution

1. Preparation

• Gather tools and parts before starting.
• Ensure the vehicle is parked on a level surface, and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Repair Intake System

• Sub-steps:

  1. Visually inspect all vacuum hoses and connections for cracks or disconnections.
  2. If leaks are found, replace damaged hoses or reattach loose connections.
  3. Check the intake manifold gasket for any signs of wear or leaks; replace if necessary.

• Tools Required:

  • Socket set
  • Screwdriver set

3. Clean or Replace MAF Sensor

• Sub-steps:

  1. Locate the MAF sensor along the air intake duct.
  2. Disconnect the electrical connector and remove the sensor using the appropriate socket.
  3. Clean the MAF sensor with MAF cleaner spray. Do not touch the sensor element.
  4. Reinstall the sensor, ensuring it is secured and the connector is reattached.

• Tools Required:

  • Torx or socket set
  • MAF cleaner spray

4. Test and Repair Fuel System

• Sub-steps:

  1. Connect a fuel pressure gauge to the fuel rail test port.
  2. Turn the ignition to the "ON" position (do not start) and check the pressure against manufacturer specifications (typically between 50-60 psi).
  3. If pressure is low, inspect the fuel pump and filter for blockages and replace if necessary.
  4. Inspect fuel injectors for clogs; clean or replace as required.

• Tools Required:

  • Fuel pressure gauge
  • Injector cleaning kit (if needed)

5. Clear Codes and Test Drive

• Sub-steps:

  1. Reconnect the negative battery terminal.
  2. Use an OBD-II scanner to clear the P0171 code.
  3. Perform a test drive to assess vehicle performance and check for reoccurrence of the code.

• Tools Required:

  • OBD-II scanner