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

Solution

1. Preparation

• Tools Required: OBD-II scanner, vacuum gauge, fuel pressure gauge, MAF cleaner, basic hand tools.
• Disconnect the battery to prevent electrical shorts during repairs.
• Allow engine to cool before beginning work.

2. Inspect and Repair Vacuum Leaks

• Visually inspect all vacuum hoses for cracks or disconnections.
• Use a vacuum gauge to check the intake manifold for leaks.
• Repair or replace any damaged hoses or gaskets found during inspection.

3. Clean or Replace MAF Sensor

• Locate the MAF sensor, which is typically situated between the air filter and throttle body.
• Disconnect the MAF sensor electrical connector.
• Use MAF cleaner to spray and clean the sensor element. Avoid touching the sensor with fingers.
• Reconnect the MAF sensor and ensure it is securely attached.

4. Check and Adjust Fuel Pressure

• Connect the fuel pressure gauge to the fuel rail.
• Turn the ignition to the "On" position (without starting the engine) to check the fuel pressure.
• Compare the reading to the manufacturer's specifications. If pressure is low, inspect the fuel pump and filter for issues.
• Replace the fuel filter if clogged, and consider replacing the fuel pump if it fails to deliver adequate pressure.

5. Inspect Fuel Injectors

• Disconnect the fuel injector connectors and remove the injectors from the fuel rail.
• Check for any clogs or debris in the injectors.
• Clean the injectors using an ultrasonic cleaner or replace them if they are damaged.

6. Final Assembly

• Reinstall all components in reverse order of removal.
• Reconnect the battery and start the engine to check for smooth operation.