my Toyota Highlander Third Generation (2014-2019) has a check engine light with code P0174

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the vehicle battery to ensure safety.
• Allow the engine to cool if necessary.

2. Inspect and Repair Air Intake System

• Tools Required: Socket set, screwdrivers, flashlight
• Sub-steps:
  1. Visually inspect the air intake hoses for any cracks or disconnections.
  2. Remove the air intake duct and check the connections at the throttle body.
  3. Replace any damaged hoses or components found during inspection.

3. Clean MAF Sensor

• Tools Required: MAF sensor cleaner, torque wrench
• Sub-steps:
  1. Locate the MAF sensor in the air intake system.
  2. Disconnect the electrical connector from the MAF sensor.
  3. Carefully remove the MAF sensor from its housing.
  4. Spray the MAF sensor with MAF sensor cleaner and allow it to dry completely.
  5. Reinstall the MAF sensor and reconnect the electrical connector.

4. Check Fuel Pressure

• Tools Required: Fuel pressure gauge
• Sub-steps:
  1. Locate the fuel rail and connect the fuel pressure gauge.
  2. Turn the ignition to the "ON" position without starting the engine and check the fuel pressure reading.
  3. If the reading is below specifications (typically around 30-50 psi), consider replacing the fuel pump or checking the fuel filter.

5. Examine Vacuum Lines

• Tools Required: Vacuum gauge, inspection tool
• Sub-steps:
  1. Visually inspect all vacuum lines connected to the intake manifold.
  2. Use a vacuum gauge to check for proper vacuum levels while the engine is running.
  3. Replace any cracked or disconnected vacuum hoses.