how to fix P0171 code on Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety during the repair process.

2. Inspect and Repair Air Intake System

• Tools Required: Socket set, screwdrivers, flashlight
• Check all connections on the air intake system, including the air filter housing and throttle body.
• Tighten any loose clamps and replace any damaged hoses or components.

3. Fuel System Check

• Tools Required: Fuel pressure gauge
• Connect the fuel pressure gauge to the fuel rail.
• Turn the ignition to the "ON" position (do not start the engine) and check the pressure reading against factory specifications (usually between 40-50 PSI for most Toyota engines).
• If low, inspect the fuel pump, fuel filter, and fuel lines for clogs or failures. Replace as needed.

4. Clean MAF Sensor

• Tools Required: MAF sensor cleaner
• Remove the MAF sensor from the air intake duct.
• Spray the cleaning solution onto the sensor element and allow it to dry completely before reinstalling it.

5. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet
• Locate the upstream (pre-catalytic converter) oxygen sensor.
• Remove the sensor using the O2 sensor socket and inspect it for damage.
• Replace the sensor if it appears faulty or if the vehicle has high mileage.

6. Check for Vacuum Leaks

• Tools Required: Smoke machine or carburetor cleaner
• Use a smoke machine to detect any vacuum leaks in the intake manifold or hoses.
• If using carburetor cleaner, carefully spray along suspected areas while the engine is running and listen for changes in engine RPM.
• Replace any faulty hoses or gaskets as necessary.