how to fix P0420 code on Honda Civic 10th Generation (2016-2021)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical short circuits.
• Allow the engine to cool down before starting work on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Tools Needed: O2 sensor socket, ratchet, torque wrench
• Remove the upstream oxygen sensor located before the catalytic converter.
• Install the new upstream oxygen sensor and torque to manufacturer specifications (typically around 30 lb-ft).
• Repeat the process for the downstream oxygen sensor if necessary.

3. Examine the Catalytic Converter

• Inspect the catalytic converter for physical damage, such as dents or rust.
• If the catalytic converter is damaged, it should be replaced.
• Tools Needed: Socket set, torque wrench
• Remove the bolts securing the catalytic converter to the exhaust system and disconnect any exhaust hangers.
• Install the new catalytic converter and torque the bolts to manufacturer specifications.

4. Check for Exhaust Leaks

• Inspect all exhaust joints and gaskets for leaks.
• Replace any damaged gaskets or use exhaust sealant as needed to ensure a proper seal.

5. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the trouble codes from the vehicle's computer.
• Perform a test drive to allow the vehicle to enter closed-loop operation and monitor for any reoccurring codes.