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

Solution

1. Preparation

• Gather all tools and parts required for repair.
• Disconnect the battery to ensure safety during repairs.
• Allow the engine to cool before starting work on the exhaust system.

2. Inspect and Test Oxygen Sensors

• Remove the oxygen sensor from the exhaust manifold (pre-catalytic).
  • Tools Required: O2 sensor socket, wrench
  • Safety Warning: Wear gloves to protect hands from exhaust residue.
• Inspect the sensor for contamination or damage.
• Use a multimeter to test the sensor's resistance and voltage output.
• If faulty, replace the sensor with a new one.

3. Replace Catalytic Converter (if necessary)

• If the catalytic converter is determined to be defective, proceed to replace it.
• Raise the vehicle using a jack and secure it with jack stands.
• Remove the bolts securing the catalytic converter to the exhaust manifold and downpipe.
  • Tools Required: Socket set, torque wrench
• Carefully detach the catalytic converter from the exhaust system.
• Install the new catalytic converter, ensuring proper alignment.
• Tighten all bolts to the manufacturer's specified torque settings.

4. Reconnect Oxygen Sensors

• Reinstall the pre-catalytic oxygen sensor into the new catalytic converter.
• If applicable, replace and reconnect the post-catalytic oxygen sensor.

5. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear the P0420 trouble code.