how to fix P0171 lean condition code on my Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

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

2. Inspect Air Intake System

• Remove the air intake duct by loosening the clamps using a screwdriver.
• Visually inspect the duct for cracks or breaks.
• Reconnect the duct and ensure it is secured properly.

3. Clean the Mass Air Flow Sensor

• Locate the MAF sensor in the air intake path.
• Remove the sensor by unscrewing it from its mounting.
• Use MAF sensor cleaner to spray the sensor elements; do not touch them.
• Allow the sensor to dry completely before reinstallation.

4. Check Fuel Pressure

• Attach a fuel pressure gauge to the Schrader valve on the fuel rail.
• Start the engine and monitor the pressure; it should meet the specifications (typically around 40-50 psi).
• If pressure is low, inspect and replace the fuel pump if necessary.

5. Inspect Fuel Injectors

• Remove the fuel rail with appropriate tools.
• Clean or replace clogged fuel injectors as needed; use an injector cleaning kit if available.
• Reinstall the fuel rail ensuring all connections are tight.

6. Check for Vacuum Leaks

• Visually inspect all vacuum hoses for cracks and ensure they are securely connected.
• Use a smoke machine or carburetor cleaner to detect leaks around gaskets and hoses.
• Replace any damaged hoses or gaskets identified during inspection.