why is my Toyota Corolla E140 (2006-2013) check engine light on P0171

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool before working on the intake system.

2. Inspect and Repair Air Intake System

• Tools Required: Socket set, vacuum gauge, MAF cleaner
• Visually inspect the air intake hoses for cracks or disconnections.
• Use a vacuum gauge to test for leaks in the intake system.
• If leaks are found, replace damaged hoses or re-seal connections.

3. Clean or Replace MAF Sensor

• Tools Required: MAF cleaner
• Remove the MAF sensor from the air intake duct.
• Spray MAF cleaner on the sensor element, avoiding physical contact.
• Allow the sensor to dry completely before reinstallation.

4. Test and Repair Fuel System

• Tools Required: Fuel pressure gauge
• Connect a fuel pressure gauge to the fuel rail.
• Turn the ignition to the "ON" position (do not start) and check the fuel pressure against specifications.
• If the pressure is low, inspect the fuel pump and filter. Replace as necessary.

5. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket
• Locate the upstream oxygen sensor (before the catalytic converter).
• Disconnect the wiring harness and unscrew the sensor using the O2 sensor socket.
• Install the new sensor, ensuring it is torqued to the manufacturer's specifications.

6. Reassemble and Reconnect Battery

• Reinstall any components removed during inspection.
• Reconnect the negative battery terminal.
• Start the engine and allow it to reach operating temperature.