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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to reset the computer.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench, OBD-II scanner
• Remove the upstream (pre-catalytic) oxygen sensor using the O2 sensor socket.
• Inspect the sensor for damage or contamination. If faulty, replace it with a new one.
• Repeat the process for the downstream (post-catalytic) oxygen sensor if it shows signs of failure.

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

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter (if applicable)
• Raise the vehicle using a jack and secure it with jack stands.
• Inspect the catalytic converter for physical damage or signs of clogging.
• If replacement is needed, unbolt the catalytic converter from the exhaust system, ensuring to remove any heat shields if present.
• Install the new catalytic converter and ensure all bolts are tightened to the manufacturer’s specifications (typically around 30-45 ft-lbs).
• Reattach any heat shields and lower the vehicle.

4. Clear Error Codes

• Tools Required: OBD-II scanner
• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the error codes from the vehicle's computer.