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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative terminal of the battery to prevent electrical shorts.

2. Inspect and Repair Air Intake System

• Tools Required: Socket set, vacuum gauge, flashlight
• Instructions:
  1. Visually inspect the air intake hose for cracks or signs of wear.
  2. Remove the air intake duct and inspect the throttle body for carbon buildup.
  3. Clean the throttle body using throttle body cleaner and a soft rag.
  4. Reconnect the air intake duct ensuring a tight fit.

3. Check and Clean MAF Sensor

• Tools Required: MAF sensor cleaner, small brush
• Instructions:
  1. Locate the MAF sensor in the air intake path.
  2. Disconnect the electrical connector from the MAF sensor.
  3. Remove the MAF sensor from its housing.
  4. Spray MAF sensor cleaner onto the sensor elements and allow it to dry.
  5. Reinstall the MAF sensor and reconnect the electrical connector.

4. Fuel Pressure Check

• Tools Required: Fuel pressure gauge
• Instructions:
  1. Locate the fuel rail on the engine.
  2. Attach the fuel pressure gauge to the service port on the fuel rail.
  3. Turn the ignition to the "ON" position without starting the engine to check pressure.
  4. Compare the reading to manufacturer specifications (typically 40-50 psi for most engines).
  5. If pressure is low, check the fuel pump and filter for issues.

5. Inspect Fuel Injectors

• Tools Required: Injector cleaning kit or multimeter
• Instructions:
  1. Disconnect the fuel injector connectors.
  2. Test each injector's resistance with a multimeter (typically 12-16 ohms).
  3. If any injector is out of spec, replace it.
  4. If all injectors are functional, consider using an injector cleaner.