how to fix P0420 code on Honda Accord Eleventh Generation (2023-present)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety.
• Allow the engine to cool down before working on the exhaust system.

2. Inspect and Replace O2 Sensors (if necessary)

• Tools Required: O2 sensor socket, wrench set, torque wrench.
• Remove the upstream O2 sensor by using an O2 sensor socket. Replace it with a new sensor if it shows signs of malfunction.
• Torque the new O2 sensor to the manufacturer's specifications (typically around 30 lb-ft).
• Repeat the process for the downstream O2 sensor if testing indicates it is faulty.

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

• Tools Required: Socket set, torch wrench, exhaust hanger removal tool.
• Remove the exhaust pipe leading to the catalytic converter by loosening the bolts at both ends.
• Use the exhaust hanger removal tool to detach the catalytic converter from its mounts.
• Inspect the old catalytic converter for internal damage or blockage. If damaged, replace it with a new one.
• Install the new catalytic converter, ensuring all gaskets are in place.
• Tighten all bolts to the specified torque.

4. Clear Codes and Test

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the ECM.
• Start the engine and let it reach operating temperature. Monitor for any codes to reappear.