how to fix P0171 code on Toyota Highlander Fourth Generation (2020-present)

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 avoid electrical shorts.

2. Inspect and Repair the Air Intake System

• Tools Required: Socket set, screwdrivers, vacuum gauge
• Remove the engine cover if necessary.
• Inspect the air intake hoses for cracks or loose connections; replace any damaged hoses.
• Check the intake manifold gasket for leaks; replace if found defective.

3. Clean or Replace the MAF Sensor

• Tools Required: MAF cleaner, torx screwdriver
• Carefully disconnect the MAF sensor connector.
• Remove the MAF sensor from its housing using a torx screwdriver.
• Clean the MAF sensor using a specialized MAF cleaner; allow it to dry completely before reinstallation.
• Reinstall the MAF sensor and reconnect the electrical connector.

4. Check and Repair the Fuel System

• Tools Required: Fuel pressure gauge, socket set
• Connect the fuel pressure gauge to the fuel rail test port.
• Turn the ignition to the "ON" position (do not start the engine) to check fuel pressure; it should meet manufacturer specifications.
• If pressure is low, inspect the fuel filter, fuel pump, and injectors for clogs or failures; replace as necessary.

5. Inspect Vacuum Lines

• Tools Required: Visual inspection tools
• Visually inspect all vacuum lines for signs of wear or damage.
• Replace any vacuum lines that are cracked or leaking.

6. Test Engine Coolant Temperature Sensor

• Tools Required: Multimeter
• Disconnect the connector from the coolant temperature sensor.
• Use a multimeter to check the resistance of the sensor according to manufacturer specifications.
• Replace the sensor if it is out of range.