what does code P0171 mean for my Toyota Highlander Third Generation (2014-2019)?

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on the vehicle.

2. Inspect and Repair Vacuum Leaks

• Inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
• Use a smoke machine or carburetor cleaner to identify leaks if necessary.
• Replace any damaged hoses or gaskets found during inspection.

3. Clean or Replace MAF Sensor

• Remove the MAF sensor from the air intake duct.
• Use MAF sensor cleaner to clean the sensor element gently. Allow it to dry completely.
• Reinstall the MAF sensor and ensure it is securely connected.

4. Check and Adjust Fuel Pressure

• Connect a fuel pressure gauge to the fuel rail service port.
• Turn the ignition on (do not start the engine) and check the pressure reading.
• If pressure is below specifications, inspect the fuel pump and filter for issues and replace as necessary.

5. Inspect Fuel Injectors

• Remove the fuel rail assembly if necessary to access the fuel injectors.
• Check the injectors for proper operation using a multimeter or an injector tester.
• Clean or replace any malfunctioning injectors.

6. Check Oxygen Sensors

• Inspect the upstream oxygen sensor for proper wiring and operation.
• Use a multimeter to test the sensor's voltage output while the engine is running.
• Replace the oxygen sensor if it is out of specifications.