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

Solution

1. Preparation

• Gather necessary tools and parts.
• Park the vehicle on a level surface and engage the parking brake.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool down before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, and wrench set.
• Steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Disconnect the electrical connectors from both sensors.
  3. Use the O2 sensor socket to carefully unscrew the sensors from the exhaust pipe.
  4. Install the new sensors by screwing them in and reconnecting the electrical connectors.
  5. Ensure the sensors are tightened to manufacturer specifications (typically around 30 lb-ft).

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, jack and jack stands, exhaust hanger removal tool.
• Steps:
  1. Raise the vehicle using a jack and secure with jack stands.
  2. Locate the catalytic converter in the exhaust system.
  3. Remove the exhaust bolts connecting the catalytic converter to the exhaust manifold and the pipe.
  4. Disconnect any exhaust hangers using the exhaust hanger removal tool.
  5. Remove the old catalytic converter and install the new one, ensuring proper alignment.
  6. Reattach exhaust bolts and tighten to manufacturer specifications (typically around 30 lb-ft).
  7. Reinstall all hangers securely.

4. Reconnect Battery and Test Drive

• Reconnect the battery terminals.
• Start the vehicle and let it idle for a few minutes.
• Take the vehicle for a test drive to ensure that the check engine light does not return.