how to fix P0174 code on Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Repair Air Intake System

• Inspect hoses and gaskets:
  • Visually check all vacuum hoses and gaskets connected to the intake manifold.
  • Replace any damaged or cracked hoses and gaskets.
• Check for loose connections:
  • Ensure that all connections are secure and tight.

3. Clean or Replace MAF Sensor

• Remove MAF sensor:
  • Disconnect the electrical connector from the MAF sensor.
  • Unscrew the sensor from the air intake duct.
• Clean the MAF sensor:
  • Use MAF sensor cleaner to spray the sensing element.
  • Allow it to dry completely before reinstallation.
• Reinstall MAF sensor:
  • Secure the sensor back to the air intake duct and reconnect the electrical connector.

4. Test and Repair Fuel System

• Check fuel pressure:
  • Connect the fuel pressure gauge to the fuel rail.
  • Start the engine and observe the pressure readings, ensuring they meet specifications (typically around 50-60 psi).
• Replace fuel filter if necessary:
  • If pressure is low, replace the fuel filter and check the fuel pump operation.

5. Inspect and Test Oxygen Sensors

• Check for proper signal:
  • Use a multimeter to test the voltage output of the upstream and downstream oxygen sensors.
  • Replace any sensors that do not meet specifications.