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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect Air Intake System

• Tools Required: Socket set, screwdrivers, flashlight
• Examine the air intake hoses for cracks or loose connections.
• Tighten or replace any damaged hoses or clamps.
• Reconnect the battery terminal when done.

3. Test Fuel Pressure

• Tools Required: Fuel pressure gauge
• Locate the fuel rail and connect the fuel pressure gauge.
• Turn the ignition to the ON position (without starting the engine) to check the fuel pressure.
• Compare the reading with the manufacturer's specifications (typically around 40-50 PSI). If low, inspect the fuel pump and filter.
• If pressure is adequate, disconnect the gauge.

4. Clean or Replace MAF Sensor

• Tools Required: MAF sensor cleaner
• Locate the MAF sensor on the air intake duct.
• Disconnect the electrical connector and remove the sensor.
• Clean the sensor gently with MAF cleaner, or replace it if damaged.
• Reinstall the MAF sensor and reconnect the electrical connector.

5. Clean Throttle Body

• Tools Required: Throttle body cleaner, soft cloth
• Remove the air intake duct to access the throttle body.
• Use throttle body cleaner to remove carbon buildup inside the throttle body.
• Wipe clean with a soft cloth, ensuring the throttle plate moves freely.
• Reassemble the air intake duct.

6. Replace Oxygen Sensor (if needed)

• Tools Required: Oxygen sensor socket
• Locate the upstream oxygen sensor on the exhaust manifold.
• Disconnect the electrical connector and unscrew the sensor using the oxygen sensor socket.
• Install the new sensor, ensuring it is properly torqued according to manufacturer specifications.
• Reconnect the electrical connector.