how to diagnose P0420 code on my Toyota Corolla E210 (2019-2024)?

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on electrical components.
• Allow the exhaust system to cool down before inspection.

2. Inspect and Replace Oxygen Sensors (if faulty)

• Tools Required: O2 sensor socket, wrench set, multimeter.
• Remove the upstream and downstream oxygen sensors using the O2 sensor socket.
• Test the sensors with a multimeter to confirm they are within specifications.
• If faulty, install new oxygen sensors by reversing the removal process, ensuring proper torque specifications (typically 30 lb-ft).

3. Inspect Catalytic Converter

• Check for any restrictions or physical damage to the catalytic converter.
• If damaged or not functioning correctly, remove the catalytic converter by unbolting it from the exhaust system.
• Replace it with a new catalytic converter, ensuring all gaskets are replaced and bolts are torqued to manufacturer specifications (typically around 30 lb-ft).

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
• Ensure all connections are secure and there are no leaks in the exhaust system.