how to fix P0171 code on Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:

  • Visually inspect all vacuum hoses connected to the intake manifold.
  • Use a smoke machine or a can of carburetor cleaner to check for leaks.
  • Replace any damaged hoses or fittings.

• Tools Required: Smoke machine or carburetor cleaner, pliers, replacement hoses

3. Clean or Replace MAF Sensor

• Sub-steps:

  • Locate the MAF sensor in the air intake duct.
  • Disconnect the electrical connector and remove the sensor.
  • Clean the MAF sensor using MAF cleaner spray (do not touch the sensing element).
  • If cleaning does not resolve the issue, replace the MAF sensor with a new one.

• Tools Required: Screwdriver, MAF cleaner, replacement MAF sensor (if necessary)

4. Test Fuel Pressure

• Sub-steps:

  • Connect a fuel pressure gauge to the fuel rail.
  • Turn the ignition to the "ON" position without starting the engine to check the fuel pressure.
  • Compare the reading with the manufacturer’s specifications (typically around 40-50 psi).
  • If pressure is low, check the fuel pump and fuel filter for issues and replace as necessary.

• Tools Required: Fuel pressure gauge

5. Inspect and Clean Fuel Injectors

• Sub-steps:

  • Remove the fuel injector rail from the engine.
  • Inspect each injector for clogs or leaks.
  • Clean the injectors using an ultrasonic cleaner or a fuel injector cleaning kit, or replace them if damaged.

• Tools Required: Fuel injector cleaning kit, ultrasonic cleaner (if available), replacement injectors (if necessary)

6. Reconnect Everything and Clear Codes

• Sub-steps:
  • Reassemble all components removed during inspection and repair.
  • Reconnect the battery.
  • Use an OBD-II scanner to clear the P0171 code from the ECM.