how to fix P0171 code on my Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

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

2. Inspect and Repair Air Intake System

• Sub-steps:
  • Visually inspect all air intake hoses and connections for cracks or loose fittings.
  • Tighten any loose clamps or connections.
  • Replace any damaged hoses with OEM parts.

3. Clean MAF Sensor

• Tools Required: MAF sensor cleaner
• Sub-steps:
  • Locate the MAF sensor in the air intake path.
  • Carefully disconnect the electrical connector.
  • Remove the sensor from the housing.
  • Spray MAF sensor cleaner onto the sensor elements and allow it to dry completely before reinstalling.

4. Check and Replace Fuel Filter (if necessary)

• Sub-steps:
  • Locate the fuel filter, typically near the fuel tank or along the fuel line.
  • Depressurize the fuel system by removing the fuel pump fuse and running the engine until it stalls.
  • Disconnect the fuel lines and remove the old filter.
  • Install the new fuel filter, ensuring correct orientation, and reconnect the fuel lines.

5. Test Fuel Pressure

• Tools Required: Fuel pressure gauge
• Sub-steps:
  • Connect the fuel pressure gauge to the fuel rail test port.
  • Turn the key to the "ON" position (not starting) to check for the specified pressure.
  • If pressure is low, further investigate the fuel pump or fuel injectors.

6. Recheck System

• Reconnect the negative battery terminal.
• Start the engine and monitor for any unusual sounds or behaviors.