my Honda Accord 10th Generation (2018-2022) has a check engine light with code P0420

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the vehicle to cool down before working on the exhaust components.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Use a wrench to carefully disconnect the electrical connectors from both sensors.
3. Remove the sensors using an oxygen sensor socket or wrench.
4. Install the new oxygen sensors by threading them into place and tightening them to the manufacturer's specifications (typically 30 lb-ft).
5. Reconnect the electrical connectors securely.

3. Inspect and Replace Catalytic Converter (if necessary)

1. If the catalytic converter is determined to be faulty, support the exhaust system with a jack or stands.
2. Remove any heat shields or brackets securing the catalytic converter.
3. Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe, using a socket set.
4. Install the new catalytic converter, ensuring proper alignment and sealing.
5. Torque the bolts to the manufacturer's specifications (usually around 30 lb-ft for connection points).
6. Reinstall any heat shields or brackets that were removed.

4. Reconnect Battery and Clear Codes

1. Reconnect the negative battery terminal.
2. Use the OBD-II scanner to clear the P0420 code from the system.
3. Start the vehicle and allow it to reach operating temperature.