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

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, fuel pressure gauge, socket set, torque wrench, cleaning supplies (MAF cleaner), and safety glasses.
• Ensure the vehicle is parked on a level surface, and the engine is cool.

2. Inspect and Repair Air Intake System

• Sub-steps:
  • Visually inspect all vacuum hoses for cracks or disconnections. Replace as necessary.
  • Remove the air intake duct and inspect for any obstructions or leaks.
  • Check the integrity of the intake manifold gaskets. Replace if any signs of wear or damage are present.

3. Clean or Replace MAF Sensor

• Sub-steps:
  • Disconnect the MAF sensor wiring harness.
  • Remove the MAF sensor using a socket set.
  • Clean the MAF sensor with MAF cleaner; allow it to dry completely before reinstalling.
  • If the sensor is faulty, replace it with a new one and reconnect the wiring harness.

4. Test and Repair Fuel Delivery System

• Sub-steps:
  • Connect the fuel pressure gauge to the fuel rail.
  • Turn the ignition to the "ON" position (without starting the engine) to check for fuel pressure; it should be within the manufacturer’s specifications (typically around 50-60 psi).
  • If fuel pressure is low, inspect the fuel pump and fuel filter for blockages or failures.
  • Check the fuel injectors for proper operation by disconnecting them and performing a resistance test with a multimeter. Replace any faulty injectors.

5. Reconnect and Test

• Sub-steps:
  • Reconnect any components that were removed during inspection and repairs.
  • Clear the DTCs using the OBD-II scanner.
  • Start the engine and monitor for any return of the P0171 code.