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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, and extension.
• Sub-steps:
  1. Remove the upstream oxygen sensor by using the O2 sensor socket.
  2. Inspect the sensor for carbon build-up or damage; replace if necessary.
  3. Repeat the process for the downstream oxygen sensor.
  4. Install the new sensors and tighten to manufacturer’s specifications (usually around 30 lb-ft).

3. Inspect the Catalytic Converter

• Tools Required: Torque wrench, pry bar.
• Sub-steps:
  1. Visually inspect the catalytic converter for cracks or damage.
  2. If any damage is found, remove the catalytic converter.
     • Use a ratchet and appropriate socket sizes to detach any bolts or clamps.
  3. If the converter is clogged, replace it with a new unit, ensuring proper fit and alignment.
  4. Torque the bolts to the manufacturer's specifications (typically around 25 lb-ft).

4. Clear Codes and Test Drive

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.
  3. Start the engine and let it reach operating temperature.
  4. Perform a test drive to ensure the check engine light does not reappear.