how to fix P0171 code on Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Vacuum gauge, screwdriver set, hose clamps.
• Inspect all vacuum hoses for cracks or disconnections.
• Tighten or replace any loose or damaged hoses.
• Use a vacuum gauge to check for leaks in the intake manifold and repair as necessary.

3. Clean or Replace MAF Sensor

• Tools Required: MAF sensor cleaner or isopropyl alcohol, torx screwdriver.
• Locate the MAF sensor in the air intake duct.
• Disconnect the electrical connector and remove the MAF sensor.
• Clean the sensor wires gently with MAF cleaner or isopropyl alcohol.
• If cleaning does not resolve the issue, replace the MAF sensor.

4. Check Fuel Pressure

• Tools Required: Fuel pressure gauge.
• Locate the fuel pressure test port on the fuel rail.
• Connect the fuel pressure gauge and turn the ignition to the "ON" position (do not start the engine).
• Check the fuel pressure against manufacturer specifications; replace the fuel pump or filter if pressure is low.

5. Inspect Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench.
• Locate the upstream oxygen sensor (pre-catalytic converter).
• Disconnect the sensor and inspect the wiring for damage.
• Test the sensor with a multimeter; replace if it is outside of specifications.
• Reinstall the sensor, applying the manufacturer-recommended torque.