how to fix P0171 code in my Toyota Corolla E140 (2006-2013)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent any electrical shorts.
• Ensure the engine is cool before beginning work.

2. Inspect and Repair Vacuum Leaks

• Visually inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
• Use a smoke machine or carburetor cleaner to detect leaks while the engine is running.
• Replace any damaged hoses or gaskets.

3. Check and Clean the Mass Airflow Sensor (MAF)

• Locate the MAF sensor on the air intake duct.
• Disconnect the electrical connector and remove the sensor.
• Clean the sensor using MAF cleaner spray; do not touch the sensor element with your fingers.
• Reinstall the MAF sensor and reconnect the electrical connector.

4. Test and Adjust Fuel Pressure

• Connect a fuel pressure gauge to the fuel rail.
• Turn the ignition to the "ON" position (do not start the engine) and check the fuel pressure reading.
• If the pressure is below specification, check the fuel filter and pump; replace if necessary.

5. Inspect Fuel Injectors

• Remove the fuel rail to access the injectors.
• Inspect injectors for clogs; clean or replace as needed.
• Reinstall the fuel rail, ensuring all connections are secure.

6. Check Engine Coolant Temperature Sensor

• Locate the coolant temperature sensor and disconnect the electrical connector.
• Use a multimeter to measure resistance; compare readings to specifications in the service manual.
• Replace the sensor if readings are out of range.

7. Reconnect Battery

• Reconnect the negative battery terminal after all repairs are complete.