how to fix P0420 code in Honda Accord Eleventh Generation (2023-present)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent any electrical issues.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench, penetrating oil
• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Apply penetrating oil to the sensor threads and allow it to sit for a few minutes.
  3. Disconnect the electrical connectors from both oxygen sensors.
  4. Use the O2 sensor socket to remove the sensors from the exhaust manifold and catalytic converter.
  5. Install the new oxygen sensors by hand to avoid cross-threading, then tighten to the manufacturer's specifications (usually around 30-40 ft-lbs).
  6. Reconnect the electrical connectors securely.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if necessary), gasket scraper
• Sub-steps:
  1. Unbolt the exhaust system from the catalytic converter.
  2. Remove any heat shields or brackets securing the catalytic converter.
  3. If necessary, cut the exhaust pipes to remove the old catalytic converter.
  4. Clean the mating surfaces on the exhaust pipes and ensure no debris is present.
  5. Install the new catalytic converter, ensuring that it is oriented correctly.
  6. Secure it with new gaskets and bolts, torquing to the specifications provided in the service manual.

4. Reassemble Exhaust System

• Sub-steps:
  1. Reattach any heat shields or brackets previously removed.
  2. Ensure all connections are tight and leak-free.
  3. Reconnect the negative battery terminal.