how to fix P0420 code on Honda Accord 8th Generation (2008-2012)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down if it has been running.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, anti-seize compound.
• Remove the upstream (pre-catalytic converter) oxygen sensor using the O2 sensor socket.
• Inspect the O2 sensor for carbon buildup or damage; if faulty, replace it with a new sensor.
• Apply anti-seize compound to the threads of the new O2 sensor before installation.
• Reinstall the O2 sensor and reconnect the wiring harness.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter (if necessary).
• Safely elevate the vehicle using jack stands to access the undercarriage.
• Inspect the catalytic converter for physical damage or signs of clogging (e.g., rattling sound).
• If replacement is necessary, disconnect the exhaust pipes on both sides of the catalytic converter.
• Remove any mounting bolts or brackets securing the catalytic converter to the vehicle.
• Install the new catalytic converter, ensuring all gaskets and seals are intact.
• Reconnect the exhaust pipes and torque the bolts to the manufacturer’s specifications.

4. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the ECU.
• Test drive the vehicle for at least 15-30 minutes under various driving conditions to monitor for any reoccurrence of the code.