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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shock.
• Allow the engine to cool before starting work.

2. Inspect and Repair Intake System

• Tools Required: Vacuum gauge, hose clamps, screwdrivers
• Inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
• If any hoses are damaged, replace them with new vacuum hoses.
• Check the intake manifold gasket for leaks and replace it if necessary.

3. Clean or Replace MAF Sensor

• Tools Required: MAF sensor cleaner, screwdriver
• Locate the MAF sensor in the air intake duct.
• Disconnect the electrical connector from the MAF sensor.
• Remove the sensor using a screwdriver.
• Clean the sensor with MAF sensor cleaner to remove dirt and debris.
• If cleaning does not resolve the issue, replace the MAF sensor with a new one.

4. Test Fuel System

• Tools Required: Fuel pressure gauge
• Connect the fuel pressure gauge to the fuel rail.
• Turn the ignition on (but do not start the engine) to check the fuel pressure.
• Compare the reading with manufacturer specifications (typically around 50-60 psi for Highlanders).
• If the pressure is low, check the fuel pump operation and replace the fuel filter if clogged.

5. Inspect Oxygen Sensors

• Tools Required: O2 sensor socket
• Locate the upstream oxygen sensor (usually before the catalytic converter).
• Disconnect the electrical connector and remove the sensor using the O2 sensor socket.
• Inspect the sensor for damage and replace it if necessary.
• Reinstall the new or cleaned sensor and reconnect the electrical connector.

6. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0171 code.
• Start the engine and perform a test drive to ensure the issue is resolved.