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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the exhaust system to cool before beginning work to avoid burns.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: Find the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Remove the sensors: Use an oxygen sensor socket to carefully unscrew both sensors from the exhaust system.
3. Install new sensors: Apply anti-seize compound to the threads of the new sensors and install them, tightening to manufacturer specifications (typically around 30 ft-lbs).
4. Reconnect electrical connectors: Ensure the connectors are firmly attached.

3. Inspect and Replace Catalytic Converter

1. Remove exhaust components: If necessary, detach any exhaust pipes connected to the catalytic converter using a socket set, noting their positions.
2. Unbolt the catalytic converter: Use a wrench to remove the bolts securing the catalytic converter to the exhaust manifold and pipes.
3. Install the new catalytic converter: Position the new catalytic converter and secure it with bolts, torquing them to manufacturer specifications (usually around 30 ft-lbs).
4. Reattach exhaust components: Reconnect any exhaust pipes and ensure all joints are sealed properly.

4. Final Checks

1. Reconnect the battery: Reattach the negative battery terminal.
2. Clear error codes: Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
3. Test drive: Take the vehicle for a test drive to ensure the check engine light does not reappear and observe for any abnormal symptoms.