what does the P0171 code mean for my Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Tools Required: OBD-II scanner, fuel pressure gauge, MAF cleaner, socket set, torque wrench, vacuum gauge.
• 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 Air Intake System

• Sub-steps:
  1. Remove the engine cover if applicable.
  2. Carefully inspect all air intake hoses for cracks or loose fittings.
  3. Tighten any loose connections and replace damaged hoses.
  4. Check the air filter and replace if dirty.

3. Test and Clean MAF Sensor

• Sub-steps:
  1. Disconnect the MAF sensor connector.
  2. Remove the MAF sensor from the air intake assembly.
  3. Use MAF cleaner to spray the sensor elements and allow it to dry completely.
  4. Reinstall the MAF sensor and reconnect the electrical connector.

4. Check and Adjust Fuel Pressure

• Sub-steps:
  1. Connect the fuel pressure gauge to the fuel rail service port.
  2. Turn the ignition to the "ON" position without starting the engine and check the pressure reading.
  3. If the pressure is low, check the fuel pump and fuel filter for issues.
  4. Replace the fuel filter if it is clogged and replace the fuel pump if necessary.

5. Inspect Fuel Injectors

• Sub-steps:
  1. Remove the fuel injectors from the fuel rail.
  2. Use a fuel injector cleaning kit to clean the injectors or replace them if they are damaged.
  3. Reinstall the fuel injectors and ensure they are properly seated.

6. Verify Vacuum Hoses

• Sub-steps:
  1. Inspect all vacuum hoses leading to the intake manifold.
  2. Replace any cracked or disconnected hoses.
  3. Use a vacuum gauge to check for proper vacuum levels at idle.