my Toyota Highlander XU70 (2020-Present) has a check engine light with code P0171

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery to ensure safety while working on the vehicle.

Tools Required:

• OBD-II scanner
• Socket set
• Torque wrench
• Multimeter
• Fuel pressure gauge
• Screwdrivers

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum lines connected to the intake manifold for cracks or disconnections.
  2. Use a smoke machine to test for vacuum leaks if visual inspection does not reveal any issues.
  3. Replace any damaged vacuum lines with OEM parts.

3. Clean or Replace MAF Sensor

• Sub-steps:
  1. Locate the MAF sensor in the air intake system.
  2. Disconnect the electrical connector and remove the sensor.
  3. Clean the MAF sensor using MAF cleaner spray, ensuring not to touch the sensing elements.
  4. If the sensor is damaged, replace it with a new one. Install the sensor back into the intake.

4. Inspect and Repair Fuel System

• Sub-steps:
  1. Connect the fuel pressure gauge to the fuel rail.
  2. Turn the ignition to the "ON" position (do not start) and check the fuel pressure against the manufacturer's specifications.
  3. If pressure is low, check the fuel pump and filter; replace as necessary.
  4. Inspect fuel injectors; clean or replace clogged injectors.

5. Reassemble and Clear Codes

• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear any stored codes from the Vehicle Control Module (VCM).