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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the vehicle battery to prevent electrical shorts.
• Ensure the vehicle is on a level surface and use jack stands if working underneath.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors: Identify the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Remove the Sensors: Use an oxygen sensor socket to carefully unscrew and remove both sensors.
3. Inspect the Sensors: Examine the sensors for any signs of damage. If they appear faulty or have high resistance readings, replace them.
4. Install New Sensors: Apply anti-seize compound on the threads of the new sensors and install them, tightening to the manufacturer's torque specifications (generally around 30 lb-ft).

3. Inspect and Replace the Catalytic Converter

1. Remove Exhaust Components: Depending on the vehicle's configuration, you may need to remove bolts from the exhaust pipe and support brackets.
2. Remove the Catalytic Converter: Unbolt the catalytic converter from the exhaust manifold and downstream exhaust pipe. Ensure any necessary gaskets are also removed.
3. Install New Catalytic Converter: Position the new catalytic converter and secure it with new gaskets and bolts, tightening to the manufacturer's specifications.
4. Reinstall Exhaust Components: Reattach any removed exhaust components and ensure everything is secured tightly.

4. Reset the Engine Control Module (ECM)

1. Reconnect the Battery: Reconnect the vehicle battery.
2. Use OBD-II Scanner: Clear the P0420 code using the OBD-II scanner.
3. Start the Engine: Allow the engine to run for a few minutes to check for any reoccurrence of the code.