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

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, infrared thermometer, socket set, torque wrench.
• Disconnect the vehicle's battery negative terminal to prevent electrical shorts.
• Allow the engine to cool down before starting work.

2. Inspect and Test Oxygen Sensors

• Remove the upstream (pre-catalytic) oxygen sensor using a socket wrench.
• Test the sensor's resistance with a multimeter according to manufacturer's specifications.
• If faulty, replace the sensor with a new one.

3. Check and Replace Catalytic Converter (if necessary)

• Tools Required: Wrench set, exhaust pipe cutter, gasket scraper.
• Remove the downstream (post-catalytic) oxygen sensor.
• Disconnect the exhaust pipe from the catalytic converter using a wrench or socket set.
• If the catalytic converter is damaged or clogged, cut the exhaust pipe before and after the converter (if necessary) and remove the converter.
• Install the new catalytic converter and connect the exhaust pipe, ensuring all connections are secure.
• Reinstall the downstream oxygen sensor.

4. Clear Codes and Test Drive

• Reconnect the battery terminal.
• Use the OBD-II scanner to clear the P0420 code.
• Test drive the vehicle for at least 20 minutes to ensure the issue is resolved and monitor for any reoccurrence of the code.