how to resolve P0171 lean condition code in Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the battery to ensure safety.
• Allow the engine to cool.

2. Inspect and Replace Vacuum Hoses

• Tools Required: Pliers, vacuum gauge.
• Check all vacuum hoses connected to the intake manifold for cracks or disconnections.
• Replace any damaged hoses with new ones, ensuring a tight fit to prevent air leaks.

3. Clean or Replace MAF Sensor

• Tools Required: MAF cleaner, torque wrench.
• Remove the MAF sensor from the air intake duct.
• Use MAF cleaner to spray and clean the sensor elements.
• Allow it to dry completely before reinstalling. If damaged, replace with a new sensor.

4. Test Fuel System

• Tools Required: Fuel pressure gauge.
• Connect the fuel pressure gauge to the fuel rail.
• Start the engine and check that the fuel pressure is within specifications (usually between 40-50 psi).
• If pressure is low, inspect the fuel pump and filter for issues and replace as necessary.

5. Inspect for Air Leaks

• Tools Required: Smoke machine (optional), basic hand tools.
• Check all connections in the air intake system for leaks, particularly after the MAF sensor.
• If leaks are detected, replace gaskets or clamps as needed.

6. Check Fuel Injectors

• Tools Required: Multimeter, injector cleaning kit (if necessary).
• Test the fuel injectors with a multimeter for proper resistance.
• If injectors are malfunctioning, replace them or clean them using an injector cleaning kit.