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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the ignition is off.
• Disconnect the negative battery terminal for safety.

2. Inspect and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses and connectors for cracks or disconnections.
  2. Use a smoke machine or carburetor cleaner to detect leaks around the intake manifold and throttle body.
  3. Replace any damaged hoses or gaskets as needed.

3. Check and Clean the MAF Sensor

• Tools Required: MAF sensor cleaner
• Sub-steps:
  1. Locate the MAF sensor in the air intake duct.
  2. Disconnect the electrical connector and remove the MAF sensor.
  3. Spray MAF sensor cleaner onto the sensor element and allow it to dry completely.
  4. Reinstall the MAF sensor and reconnect the electrical connector.

4. Inspect and Test Fuel System

• Tools Required: Fuel pressure gauge
• Sub-steps:
  1. Locate the fuel rail and connect the fuel pressure gauge.
  2. Turn the ignition on (do not start) to check fuel pressure; it should meet manufacturer specifications (typically 50-60 psi).
  3. If pressure is low, check the fuel pump and filter for blockage or failure. Replace as necessary.

5. Inspect and Test Oxygen Sensors

• Sub-steps:
  1. Locate the upstream oxygen sensor before the catalytic converter.
  2. Use a multimeter to check the voltage output (should fluctuate between 0.1 to 0.9 volts).
  3. If the readings are outside this range, consider replacing the sensor.