how to fix P0171 lean condition in Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery to ensure safety.

2. Inspect Air Intake System

• Tools Required: Screwdriver set, flashlight
• Inspect all hoses and connections for cracks or disconnections.
• Tighten or replace any loose or damaged hoses.

3. Test Fuel Pressure

• Tools Required: Fuel pressure gauge
• Locate the fuel rail service port and connect the gauge.
• Turn the ignition to the "On" position (do not start the engine) and check the pressure. It should be within the specified range (around 50-60 psi for Highlander).
• If pressure is low, check the fuel pump operation and replace if necessary.

4. Clean or Replace MAF Sensor

• Tools Required: MAF cleaner
• Disconnect the MAF sensor electrical connector.
• Remove the sensor from the intake tube.
• Spray MAF cleaner on the sensor element and allow it to dry before reinstallation.

5. Inspect Fuel Injectors

• Tools Required: Multimeter, injector cleaner
• Use a multimeter to check the resistance of each fuel injector (should typically be around 12-16 ohms).
• If any injector is out of specification, replace it.
• If injectors are dirty, use an injector cleaning kit to clean them.

6. Replace Engine Coolant Temperature Sensor (if faulty)

• Tools Required: Socket set
• Locate the sensor (usually near the thermostat housing).
• Disconnect the electrical connector and remove the old sensor.
• Install the new sensor and reconnect the connector.