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

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, jack and jack stands.
• Safety Warnings: Disconnect the battery before starting work on the exhaust system. Allow the engine to cool completely before touching any components.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Disconnect the electrical connectors from both oxygen sensors.
3. Use a socket wrench to unscrew the sensors from the exhaust pipes.
4. Install new oxygen sensors by reversing the removal steps, ensuring they are tightened to the manufacturer's torque specifications (typically 30-40 ft-lbs).
5. Reconnect the electrical connectors to the new sensors.

3. Inspect and Replace Catalytic Converter

1. If the oxygen sensors are functioning properly, check the catalytic converter.
2. Remove the exhaust heat shield if present by unscrewing any bolts or clips.
3. Use a socket wrench to unbolt the catalytic converter from the exhaust manifold and exhaust pipe.
4. Replace with a new catalytic converter, ensuring proper alignment and fit.
5. Torque the bolts to the manufacturer's specifications (typically around 30-40 ft-lbs).
6. Reinstall the heat shield if removed.

4. Reset the Engine Control Module (ECM)

1. Reconnect the battery.
2. Use the OBD-II scanner to clear the P0420 code from the ECM.
3. Start the engine and allow it to reach operating temperature.