my Toyota Corolla E140 (2006-2013) has a P0171 code, how do I fix it?

Solution

1. Preparation

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

2. Inspect for Vacuum Leaks

• Visually check all vacuum hoses connected to the intake manifold for cracks or disconnections.
• Use a smoke machine or carburetor cleaner to detect leaks. Apply around suspected areas and check for RPM changes.

3. Clean or Replace MAF Sensor

• Remove the MAF sensor from the air intake duct.
• Use MAF sensor cleaner to spray the sensor elements carefully. Do not touch them with fingers or tools.
• Allow it to dry completely before reinstalling. If cleaning does not resolve the issue, replace the MAF sensor.

4. Check Fuel Pressure

• Connect the fuel pressure gauge to the fuel rail test port.
• Turn the ignition to the "ON" position (do not start) and check the pressure reading.
• It should be within manufacturer specifications (usually around 35-50 psi). If low, check the fuel pump and filter.

5. Inspect Fuel Injectors

• Remove the fuel rail and inspect the injectors for any signs of clogging or leaks.
• If the injectors are clogged, clean them using a professional injector cleaner or replace them if necessary.

6. Replace ECT Sensor (if faulty)

• Locate the ECT sensor on the engine block.
• Disconnect the electrical connector and remove the sensor using a socket.
• Install the new ECT sensor and reconnect the electrical connector.