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

Solution

1. Preparation

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

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors on the exhaust manifold and after the catalytic converter.
  2. Disconnect the wiring harness from each oxygen sensor.
  3. Use an oxygen sensor socket to remove the sensors from their threaded positions.
  4. Install new oxygen sensors by threading them into place and tightening them to the manufacturer’s specifications (typically 30 lb-ft).
  5. Reconnect the wiring harness to each sensor.

3. Check and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. Inspect the catalytic converter for signs of damage or blockages.
  2. If replacement is needed, remove the exhaust pipes connected to the catalytic converter using a socket set.
  3. Unbolt the catalytic converter from the exhaust manifold and remove it from the vehicle.
  4. Install the new catalytic converter in the reverse order of removal, ensuring all gaskets are replaced and connections are secure.
  5. Torque all bolts to the manufacturer’s specifications.

4. Clear Codes and Test Drive

• 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. Take the vehicle for a test drive to ensure the check engine light does not reappear and monitor performance.