how to fix P0420 code on Honda Accord 9th Generation (2013-2017)

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down before starting work.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench, lubricant.
• Remove the upstream oxygen sensor (pre-catalytic converter) using the O2 sensor socket.
• Inspect the sensor for carbon buildup or damage; replace if necessary.
• Install the new sensor, ensuring it is torqued to the manufacturer’s specifications (typically around 30 ft-lbs).
• Repeat the process for the downstream oxygen sensor (post-catalytic converter) if it was found faulty.

3. Repair or Replace Catalytic Converter

• Tools Required: Socket set, exhaust pipe cutter, clamps, gaskets.
• If the catalytic converter is damaged or not functioning, remove it by cutting the exhaust pipes with an exhaust pipe cutter.
• Ensure all gaskets and seals are in good condition; replace them if necessary.
• Install the new catalytic converter and secure it with clamps. Torque the bolts to the manufacturer's specifications.
• Reconnect all exhaust components and ensure there are no leaks.

4. Clear Codes and Test

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the system.
• Start the engine and allow it to reach operating temperature.
• Perform a test drive to ensure the check engine light does not reappear.