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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to prevent electrical shock.
• Allow the engine to cool completely before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Use an O2 sensor socket to remove the upstream oxygen sensor.
  3. Install the new sensor, ensuring it is properly torqued to manufacturer specifications (usually around 30 lb-ft).
  4. Repeat the process for the downstream oxygen sensor if it shows abnormal readings during diagnostics.

3. Inspect and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. Remove any heat shields covering the catalytic converter using a socket set.
  2. Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe.
  3. Inspect the gasket surfaces for damage; replace gaskets if necessary.
  4. Install the new catalytic converter, ensuring proper alignment and torque specifications are followed (typically 25 lb-ft).
  5. Reinstall any heat shields that were removed.

4. Clear Codes and Test

• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code from the ECM.
  3. Start the engine and allow it to reach operating temperature.
  4. Take the vehicle for a test drive to ensure proper operation and monitor for any reoccurrence of the check engine light.