why does my Toyota Corolla E210 (2019-2024) have a check engine light with code P0171?

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface, and the engine is cool.

2. Inspect and Repair Air Intake System

• Check for Leaks:
  • Visually inspect all air intake hoses and connections.
  • Use a smoke machine or soapy water to identify any leaks.
• Repair/Replace:
  • Tighten loose connections or replace damaged hoses as necessary.

3. Clean or Replace MAF Sensor

• Removal:
  • Disconnect the negative battery terminal.
  • Remove the MAF sensor connector.
  • Unscrew and remove the MAF sensor from the air intake.
• Cleaning:
  • Use MAF cleaner spray to clean the sensor elements carefully.
  • Allow it to dry completely before reinstallation.
• Reinstallation:
  • Install the MAF sensor back in the air intake and reconnect the electrical connector.

4. Check and Adjust Fuel Pressure

• Testing:
  • Connect the fuel pressure gauge to the fuel rail.
  • Turn the ignition key to the "ON" position (do not start the engine) and check the fuel pressure reading.
• Adjustment:
  • If the fuel pressure is below specifications, inspect the fuel pump and fuel filter for issues and replace them if necessary.

5. Inspect and Clean Throttle Body

• Removing Throttle Body:
  • Disconnect the throttle body electrical connector and any vacuum lines.
  • Unbolt and remove the throttle body from the intake manifold.
• Cleaning:
  • Use throttle body cleaner and a soft cloth to remove carbon deposits from the throttle plate and body.
• Reinstallation:
  • Reinstall the throttle body and reconnect all components.