how to diagnose P0171 lean code in Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal.
• Prepare the work area for accessing the engine components.

2. Inspect Air Intake System

• Check all hoses and connections from the air filter to the throttle body for cracks or disconnections.
• Repair or replace any damaged hoses or intake components.
• Tools Required: Socket set, screwdrivers.

3. Check and Clean MAF Sensor

• Remove the MAF sensor from the air intake duct.
• Use MAF sensor cleaner to clean the sensor element carefully.
• Reinstall the MAF sensor and secure it properly.
• Tools Required: Torx or socket wrench, MAF cleaner.

4. Fuel System Inspection

• Use a fuel pressure gauge to check the fuel pressure at the fuel rail.
• If the pressure is low, check the fuel pump operation and inspect the fuel filter for clogs.
• Replace the fuel filter if necessary and repair or replace the fuel pump if faulty.
• Tools Required: Fuel pressure gauge, socket set.

5. Oxygen Sensor Check

• Use a multimeter to test the voltage output of the upstream oxygen sensor.
• Replace the sensor if it is not providing the correct voltage readings.
• Tools Required: Multimeter, socket set.

6. Engine Coolant Temperature Sensor Check

• Locate the engine coolant temperature sensor and test its resistance with a multimeter.
• Replace the sensor if readings are out of specification.
• Tools Required: Multimeter, socket set.