how to diagnose P0420 code on Honda Pilot YF4 (2023-Present)

Solution

1. Preparation

• Gather tools and parts before starting the repair.
• Disconnect the battery negative terminal for safety.
• Tools required: OBD-II scanner, multimeter, socket set, torque wrench.

2. Replace Faulty Oxygen Sensors

1. Locate the upstream and downstream oxygen sensors on the exhaust system.
2. Disconnect the electrical connectors from both sensors.
3. Using a socket wrench, remove the sensors from the exhaust pipes.
4. Install new oxygen sensors, ensuring they are properly seated.
5. Torque the sensors to the manufacturer's specifications (typically around 30-40 ft-lbs).
6. Reconnect the electrical connectors.

3. Replace Catalytic Converter (if necessary)

1. If the catalytic converter is determined to be faulty, proceed with replacement.
2. Disconnect the exhaust system from the catalytic converter using a socket set.
3. Remove any mounting brackets or heat shields as needed.
4. Remove the old catalytic converter.
5. Install the new catalytic converter, ensuring proper alignment with the exhaust system.
6. Reattach all bolts and brackets, torquing them to the specified values.
7. Reconnect any oxygen sensors if they were removed.

4. Clear Codes and Test

1. Reconnect the battery negative terminal.
2. Use the OBD-II scanner to clear the P0420 code.
3. Start the engine and allow it to reach operating temperature.
4. Take the vehicle for a test drive to ensure the check engine light does not reappear and the vehicle operates normally.