how to fix the P0174 code in my Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

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

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
  2. Use a smoke machine or propane enrichment method to identify leaks.
  3. Replace any damaged hoses or gaskets as necessary.

Tools Required: Smoke machine or propane torch, pliers.

3. Clean or Replace MAF Sensor

• Sub-steps:
  1. Locate the MAF sensor on the air intake duct.
  2. Disconnect the electrical connector and remove the sensor from the duct.
  3. Clean the sensor with MAF cleaner or replace it if damaged.
  4. Reinstall the MAF sensor and reconnect the electrical connector.

Tools Required: Screwdriver set, MAF cleaner.

4. Check Fuel Pressure

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail test port.
  2. Turn the ignition key to the “On” position (do not start) and observe the fuel pressure reading.
  3. Compare the reading to manufacturer specifications (typically around 50-60 psi for many vehicles).
  4. If pressure is low, check the fuel pump and fuel filter for issues.

Tools Required: Fuel pressure gauge.

5. Inspect Fuel Injectors

• Sub-steps:
  1. Remove the fuel rail from the engine.
  2. Inspect each injector for clogs or leaks.
  3. Clean the injectors using a specialized injector cleaning kit or replace them if necessary.
  4. Reinstall the fuel rail and reconnect fuel lines.

Tools Required: Injector cleaning kit, socket set.

6. Test Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors.
  2. Use a multimeter to check the voltage output of each sensor (should fluctuate between 0.1V to 0.9V).
  3. Replace any faulty oxygen sensors.

Tools Required: Multimeter, socket set.