how to fix Honda Accord 10th Generation (2018-2022) P0420 code

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery negative terminal to prevent electrical shorts.
• Allow the exhaust system to cool before starting work.

2. Inspect and Replace Oxygen Sensors

• Inspect:

  • Remove the upstream and downstream oxygen sensors using an oxygen sensor socket.
  • Check for carbon buildup or damage on the sensor tips.

• Replace:

  • If sensors are faulty, install new OEM or high-quality replacement oxygen sensors.
  • Torque the sensors to the manufacturer's specification (typically around 30 Nm).

3. Inspect and Replace Catalytic Converter

• Remove:

  • Unbolt the catalytic converter from the exhaust system using a socket set.
  • Carefully lower the converter, ensuring no bolts or gaskets are lost.

• Inspect:

  • Check for any signs of physical damage, such as dents or holes, and look for internal clogs.

• Replace:

  • If damaged, install a new catalytic converter, ensuring it meets OEM specifications.
  • Torque all bolts to the manufacturer’s specifications.

4. Reassemble and Reconnect

• Reinstall any components removed during the inspection and repair process.
• Reconnect the battery negative terminal.

5. Clear Codes and Test Drive

• Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.
• Test drive the vehicle to ensure the check engine light does not reappear.