how to fix P0171 code in Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather required tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool before proceeding with repairs.

2. Inspect and Repair Air Intake System

• Sub-steps:
  1. Remove the air filter housing and inspect the air filter. Replace if clogged.
  2. Visually inspect all intake hoses for cracks or disconnections, and replace as necessary.
  3. Check the throttle body for carbon buildup and clean if needed using throttle body cleaner.

3. Clean or Replace MAF Sensor

• Sub-steps:
  1. Disconnect the electrical connector from the MAF sensor.
  2. Remove the MAF sensor from the intake duct.
  3. Clean the sensor using MAF cleaner and let it dry completely before reinstallation.
  4. Reinstall the sensor and reconnect the electrical connector.

4. Check and Repair Fuel System

• Sub-steps:
  1. Using a fuel pressure gauge, connect it to the fuel rail and turn the ignition on (do not start the engine) to check for fuel pressure.
  2. If pressure is low, inspect the fuel pump, fuel filter, and fuel lines for blockages or damage.
  3. Test the fuel injectors using a multimeter to ensure they are receiving the correct voltage and are functioning properly.

5. Verify Coolant Temperature Sensor

• Sub-steps:
  1. Locate the engine coolant temperature sensor and inspect its wiring for damage.
  2. Use a multimeter to check the sensor's resistance and compare it to manufacturer specifications.
  3. Replace the sensor if it is outside of specifications.

6. Exhaust System Inspection

• Sub-steps:
  1. Inspect the exhaust system for any visible leaks or damage.
  2. Check the exhaust manifold and gaskets for integrity.
  3. Repair or replace any damaged components as necessary.