how to fix P0420 code on Honda Civic 10th Generation (2016-2021)

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 battery to avoid 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. Remove the electrical connectors from both sensors.
  3. Use an oxygen sensor socket to unscrew and remove the sensors.
  4. Install the new oxygen sensors by screwing them into place, ensuring they are secure but not overtightened.
  5. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter

• Sub-steps:
  1. Locate the catalytic converter in the exhaust system.
  2. Inspect for any signs of physical damage or blockage; if damaged, proceed to replace it.
  3. Use a socket set to unbolt the catalytic converter from the exhaust pipes.
  4. Remove the old catalytic converter and install the new one, ensuring a proper fit.
  5. Torque the bolts to the manufacturer’s specifications (typically around 30-40 lb-ft).

4. Final Checks

• Sub-steps:
  1. Reconnect the battery.
  2. Start the engine and let it reach operating temperature.
  3. Clear the error codes using the OBD-II scanner.
  4. Monitor the engine for any new codes or abnormalities.