why does my Toyota Highlander Third Generation (2014-2019) have a check engine light and code P0171

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety.
• Allow the engine to cool before starting work.

2. Inspect and Repair Air Intake System

• Sub-step 1: Visually inspect all air intake hoses for cracks or loose connections.
• Sub-step 2: If leaks are found, replace the damaged hoses.
• Sub-step 3: Check the intake manifold gasket for leaks and replace if necessary.

3. Check and Clean MAF Sensor

• Sub-step 1: Remove the MAF sensor from the air intake duct.
• Sub-step 2: Use MAF cleaner to spray the sensor elements, avoiding physical contact.
• Sub-step 3: Reinstall the MAF sensor securely to the intake duct.

4. Test and Replace Fuel Pressure Regulator (if necessary)

• Sub-step 1: Connect the fuel pressure gauge to the fuel rail test port.
• Sub-step 2: Start the engine and monitor the fuel pressure; it should meet manufacturer specifications (typically around 50-60 psi).
• Sub-step 3: If pressure is low, replace the fuel pressure regulator and recheck.

5. Inspect and Clean Fuel Injectors

• Sub-step 1: Remove the fuel rail to access the injectors.
• Sub-step 2: Inspect the injectors for clogs and clean them using an injector cleaning kit.
• Sub-step 3: Reinstall the fuel rail and ensure all connections are secure.