how to fix P0420 code in 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 vehicle to cool down completely before working on the exhaust system to avoid burns.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors: Identify the upstream (before the catalytic converter) and downstream (after the catalytic converter) oxygen sensors.
2. Remove the Sensors: Use an oxygen sensor socket to unscrew the sensors from their respective locations.
3. Inspect the Sensors: Check for any signs of damage or contamination on the sensors.
4. Install New Sensors: Apply anti-seize compound to the threads of the new sensors and install them, tightening to the manufacturer’s specified torque (typically around 30 lb-ft).
5. Reconnect Electrical Connectors: Ensure all electrical connectors are secure.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove Exhaust Components: If the catalytic converter is damaged, unbolt the exhaust components leading to it using a socket set.
2. Remove the Catalytic Converter: Unscrew the bolts securing the catalytic converter to the exhaust system; gently remove it.
3. Install New Catalytic Converter: Position the new catalytic converter and secure it with bolts. Torque to the manufacturer's specifications (usually around 25 lb-ft).
4. Reattach Exhaust Components: Reconnect all previously removed components and ensure a tight fit to avoid leaks.

4. Clear Codes and Test Drive

1. Reconnect Battery: Reconnect the negative battery terminal.
2. Clear Codes: Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
3. Test Drive: Drive the vehicle for a minimum of 20 minutes to allow the engine to reach operating temperature and to monitor for any reoccurrence of the code.