how to fix P0171 code in Toyota Corolla E170 (2013-2019)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool completely before beginning work.

2. Inspect and Repair Vacuum Leaks

• Tools Required: Vacuum gauge, hose clamp pliers
• Inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
• Use a vacuum gauge to check the intake manifold vacuum; it should read within the normal range.
• Replace any damaged hoses or clamps.

3. Clean or Replace the Mass Airflow Sensor (MAF)

• Tools Required: MAF cleaner, Torx screwdriver
• Locate the MAF sensor on the air intake duct.
• Disconnect the electrical connector and remove the sensor using a Torx screwdriver.
• Clean the sensor with MAF cleaner and let it dry completely before reinstalling.
• If the sensor is damaged, replace it with a new one.

4. Check Fuel System

• Tools Required: Fuel pressure gauge
• Connect the fuel pressure gauge to the fuel rail.
• Turn the ignition to the "ON" position (without starting the engine) to check the fuel pressure.
• Compare the reading to the manufacturer specifications (typically around 43-50 psi).
• If the pressure is low, check the fuel pump and replace the fuel filter if clogged.

5. Inspect Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench
• Locate the upstream oxygen sensor (pre-catalytic converter).
• Use an O2 sensor socket to remove the sensor and inspect it for carbon buildup or damage.
• Replace the sensor if necessary and torque it to manufacturer specifications (usually around 30 lb-ft).