how to fix P0174 code in my Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool before working on components.

2. Inspect for Vacuum Leaks

• Inspect all vacuum hoses connected to the intake manifold.
  • Look for cracks or disconnections.
  • Replace any damaged hoses.
• Check the intake manifold gasket for leaks.
  • Use a smoke machine or carburetor cleaner to identify leaks.

3. Check and Clean the MAF Sensor

• Locate the MAF sensor on the intake duct.
• Remove the sensor by unscrewing it from the housing.
• Clean the sensor using MAF cleaner.
  • Spray cleaner on the sensor elements without touching them.
• Reinstall the MAF sensor securely.

4. Test Fuel Pressure

• Connect a fuel pressure gauge to the fuel rail.
• Turn the ignition to the "ON" position (do not start the engine) and observe the pressure reading.
  • Compare the reading to manufacturer specifications (typically 50-60 psi).
• If pressure is low, inspect the fuel pump and fuel filter for issues.

5. Inspect Oxygen Sensors

• Locate the upstream and downstream oxygen sensors.
• Use a multimeter to check their voltage output.
  • A properly functioning sensor should oscillate between 0.1V and 0.9V.
• Replace any faulty sensors.

6. Reassemble and Reconnect

• Reconnect any components that were removed during inspections.
• Reconnect the battery terminal securely.
• Clear the P0174 code using the OBD-II scanner.