how to fix P0420 code on Honda Accord Eleventh Generation (2023-present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative terminal of the battery to prevent accidental electrical shorts.

2. Inspect and Repair Exhaust Leaks

• Tools Required: Socket set, exhaust leak detector, gasket scraper
• Inspect the exhaust manifold, piping, and joints for leaks.
• Replace any damaged gaskets and tighten connections as necessary.

3. Replace Faulty Oxygen Sensors

• Tools Required: O2 sensor socket or wrench, penetrating oil (if sensors are rusted)
• Remove the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
• Install new oxygen sensors, ensuring they are properly torqued according to manufacturer specifications.

4. Clean or Replace the Catalytic Converter

• Tools Required: Wrench set, catalytic converter cleaner (if cleaning), or new catalytic converter
• If cleaning, use a catalytic converter cleaner according to the product instructions and run the engine to circulate the cleaner.
• If replacement is necessary, unbolt the catalytic converter from the exhaust system and install the new unit, ensuring all bolts are tightened to the specified torque.

5. Reconnect Battery and Clear Codes

• Reconnect the negative terminal of the battery.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's memory.