how to diagnose P0420 code on my Honda Accord 10th Generation (2018-2022)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is on a flat surface and engage the parking brake.
• Disconnect the negative battery terminal to prevent electrical issues while working.

2. Inspect and Replace Oxygen Sensors

1. Locate the pre-catalytic converter oxygen sensor and the post-catalytic converter sensor.
2. Use a socket wrench to remove the old oxygen sensors.
3. Install the new oxygen sensors, ensuring they are torqued to the manufacturer's specifications (typically around 30 ft-lbs).
4. Reconnect the electrical connectors for the sensors.

3. Inspect and Replace the Catalytic Converter (if necessary)

1. Remove any heat shields or brackets securing the catalytic converter.
2. Use a socket set to unbolt the catalytic converter from the exhaust system.
3. Inspect the old catalytic converter for physical damage or clogging.
4. Install the new catalytic converter, ensuring it is properly aligned and secured.
5. Reinstall any heat shields or brackets removed during the process.

4. Clear Codes and Test Drive

1. Reconnect the negative battery terminal.
2. Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.
3. Start the engine and allow it to reach operating temperature.
4. Take the vehicle for a test drive to ensure the check engine light does not reappear.