how to fix P0171 in Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

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

2. Inspect and Repair Air Intake System

• Tools Required: Socket set, screwdriver, vacuum gauge
• Inspect all air intake hoses for cracks or disconnections.
  • If any hoses are damaged, replace them.
• Check the intake manifold for any signs of leaks using a vacuum gauge.
  • If leaks are detected, re-seal or replace the manifold gasket as needed.

3. Clean or Replace MAF Sensor

• Tools Required: MAF sensor cleaner
• Disconnect the MAF sensor electrical connector.
• Remove the MAF sensor from the air intake.
• Clean the sensor with MAF cleaner and allow it to dry.
• If the sensor is faulty, replace it with a new one.

4. Check and Repair Fuel System

• Tools Required: Fuel pressure gauge, injector cleaner
• Connect the fuel pressure gauge to the fuel rail.
• Check the fuel pressure against manufacturer specifications.
  • If low, inspect the fuel pump and filter. Replace as needed.
• Use injector cleaner to clean fuel injectors if they are clogged.

5. Inspect Oxygen Sensors

• Tools Required: Socket set
• Locate the upstream oxygen sensor.
• Inspect the wiring and connector for damage.
• Test the oxygen sensor with a multimeter; replace if it is not functioning within specifications.

6. Replace Engine Coolant Temperature Sensor (if necessary)

• Tools Required: Socket set
• Locate the coolant temperature sensor.
• Disconnect the electrical connector and remove the sensor.
• Install the new sensor and reconnect the wiring.