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

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, jack and jack stands, safety glasses, gloves.
• Safety Warnings: Disconnect the battery before working on electrical systems. Allow the engine to cool before starting repairs.

2. Replace Faulty Oxygen Sensors (if necessary)

1. Remove the engine cover (if applicable) to access the oxygen sensors.
2. Disconnect the electrical connectors from the upstream and downstream oxygen sensors.
3. Use a socket wrench to unscrew the oxygen sensors from the exhaust manifold and catalytic converter.
4. Install the new oxygen sensors, ensuring they are tightened to the manufacturer's specifications (typically around 30 lb-ft).
5. Reconnect the electrical connectors to the oxygen sensors.

3. Inspect and Replace the Catalytic Converter (if necessary)

1. Raise the vehicle with a jack and secure it with jack stands.
2. Disconnect the exhaust pipes from the catalytic converter by removing any clamps or bolts.
3. Remove the old catalytic converter by unscrewing the bolts holding it in place.
4. Clean the mating surfaces on the exhaust system to ensure a proper seal for the new catalytic converter.
5. Install the new catalytic converter and secure it with bolts, tightening them to the specified torque (usually around 40 lb-ft).
6. Reconnect the exhaust pipes and ensure all clamps are secure.

4. Clear Codes and Test Drive

1. Reconnect the battery and use the OBD-II scanner to clear the P0420 code from the ECU.
2. Start the engine and allow it to reach operating temperature.
3. Take the vehicle for a test drive to ensure the check engine light does not reappear and assess vehicle performance.