why does my Honda Accord 10th Generation (2018-2022) keep throwing P0420 code

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, infrared thermometer, jack stands, and safety goggles.
• Ensure the vehicle is parked on a level surface and the engine is cool.

2. Inspect and Replace Oxygen Sensors

• 2.1. Disconnect the battery.
  • Remove the negative terminal to prevent electrical shorts.
• 2.2. Locate the oxygen sensors.
  • Find and identify the pre-catalytic and post-catalytic oxygen sensors.
• 2.3. Remove the old sensors.
  • Use an oxygen sensor socket to carefully unscrew the sensors from their respective locations.
• 2.4. Install new sensors.
  • Apply anti-seize compound to the threads of the new sensors and screw them in place. Torque to manufacturer specifications (typically around 30 lb-ft).

3. Inspect and Replace Catalytic Converter (if necessary)

• 3.1. Remove the exhaust components.
  • Use a socket set to disconnect the exhaust pipes from the catalytic converter. Support the exhaust system as needed.
• 3.2. Remove old catalytic converter.
  • Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe. Carefully take it out.
• 3.3. Install the new catalytic converter.
  • Position the new catalytic converter and bolt it back into place, ensuring proper alignment. Torque bolts to manufacturer specifications.

4. Clear Codes and Test Drive

• 4.1. Reconnect the battery.
  • Reattach the negative terminal.
• 4.2. Use the OBD-II scanner.
  • Clear the P0420 code and any other stored codes.
• 4.3. Test drive the vehicle.
  • Drive the vehicle for a minimum of 20 minutes under various conditions to allow the ECU to recalibrate.