how to fix P0171 code in my Toyota Highlander Third Generation (2014-2019)?

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent any electrical issues.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Vacuum gauge, hose clamp pliers
• Use a vacuum gauge to check for leaks.
• Inspect all vacuum hoses and connections. Replace any damaged hoses.
• Check the intake manifold gasket for signs of wear or leaks; replace if necessary.

3. Clean or Replace MAF Sensor

• Tools Required: MAF cleaner, screwdrivers
• Remove the MAF sensor from its housing.
• Spray the MAF cleaner onto the sensor element, avoiding contact with other components.
• Allow it to dry completely, then reinstall. If damaged, replace with a new MAF sensor.

4. Check and Repair Fuel System

• Tools Required: Fuel pressure gauge
• Connect the fuel pressure gauge to the fuel rail.
• Turn the ignition to the "ON" position (without starting) and check the pressure.
• If pressure is low, inspect the fuel pump and fuel filter for issues and replace if necessary.

5. Replace Engine Coolant Temperature Sensor (if faulty)

• Tools Required: Socket set, replacement sensor
• Locate the engine coolant temperature sensor, typically near the thermostat housing.
• Disconnect the electrical connector and remove the sensor.
• Install the new sensor and reconnect the wiring.

6. Reset the Engine Control Module (ECM)

• Reconnect the battery and use the OBD-II scanner to clear the P0171 code.
• Start the engine and allow it to reach operating temperature.