how to fix P0420 code in Honda Accord 10th Generation (2018-2022) catalytic converter issue

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery (negative terminal).
• Allow the engine to cool down completely.

2. Remove Exhaust Components

• Tools Required: Socket set, wrench, penetrating oil.
• Sub-steps:
  1. Apply penetrating oil to exhaust nuts/bolts to prevent stripping.
  2. Remove the bolts securing the exhaust pipe to the catalytic converter.
  3. Unclip any hangers or brackets that hold the exhaust system in place.
  4. Carefully lower the exhaust system to access the catalytic converter.

3. Inspect and Replace Catalytic Converter

• Tools Required: Torque wrench, gasket scraper.
• Sub-steps:
  1. Visually inspect the catalytic converter for signs of damage or clogging.
  2. If replacement is necessary, remove the old catalytic converter by unbolting it from the exhaust manifold and the exhaust pipe.
  3. Clean the mounting surfaces with a gasket scraper to ensure a proper seal.
  4. Install the new catalytic converter, ensuring proper alignment with the exhaust system.
  5. Torque the bolts to the manufacturer's specifications (usually around 30-40 lb-ft, check service manual for specifics).

4. Replace Oxygen Sensors (if necessary)

• Tools Required: Oxygen sensor socket, torque wrench.
• Sub-steps:
  1. Remove the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors by unscrewing them.
  2. Install the new oxygen sensors, ensuring they are properly seated.
  3. Torque the oxygen sensors to the manufacturer's specifications (usually around 30 lb-ft, verify in service manual).

5. Reassemble Exhaust Components

• Tools Required: Socket set, torque wrench.
• Sub-steps:
  1. Reattach the exhaust system, aligning all parts correctly.
  2. Tighten all bolts to the specified torque.
  3. Reinstall any hangers or brackets that were removed.

6. Final Checks

• Reconnect the battery.
• Start the engine and check for leaks.
• Allow the engine to reach operating temperature.