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

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, socket set, torque wrench, and safety goggles.
• Ensure the vehicle is parked on a level surface and the engine is cool.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Disconnect the battery to prevent electrical shorts.
  2. Remove the oxygen sensor from the exhaust manifold (upstream) using a socket wrench.
  3. Remove the downstream oxygen sensor from the catalytic converter.
  4. Install the new oxygen sensors by threading them into the exhaust system, and tighten to the manufacturer’s specifications (usually around 30 lb-ft).
  5. Reconnect the battery.

3. Inspect and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. If the catalytic converter is found to be clogged or damaged, begin by disconnecting the exhaust system from the catalytic converter.
  2. Remove the mounting bolts securing the catalytic converter using a socket set.
  3. Carefully remove the catalytic converter from its position.
  4. Install the new catalytic converter, ensuring proper alignment with exhaust flanges.
  5. Tighten all bolts to the manufacturer's torque specifications (typically 25-30 lb-ft).
  6. Reconnect the exhaust system and check for leaks.

4. Clear Codes and Test Drive

• Sub-steps:
  1. Use the OBD-II scanner to clear any trouble codes from the vehicle’s computer.
  2. Conduct a test drive under various driving conditions to ensure the vehicle operates smoothly without the check engine light reappearing.