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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Unplug the electrical connectors from both oxygen sensors.
  3. Use an O2 sensor socket to remove the upstream sensor, followed by the downstream sensor.
  4. Install the new oxygen sensors by threading them into place and tightening to manufacturer specifications (typically 30 lb-ft).
  5. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. Visually inspect the catalytic converter for signs of damage like dents or rust.
  2. If damaged, remove the exhaust pipes connected to the catalytic converter using a socket set.
  3. Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe.
  4. Install the new catalytic converter, ensuring it aligns properly with the exhaust system.
  5. Tighten all bolts to the manufacturer's torque specifications (usually around 30 lb-ft for flange bolts).
  6. Reconnect any exhaust hangers and ensure there are no leaks.

4. Clear Codes and Test Drive

• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code.
  3. Start the engine and allow it to reach normal operating temperature.
  4. Take the vehicle for a test drive to ensure that the check engine light does not return.