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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety during repairs.
• Allow the vehicle to cool down completely if the engine has been running.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, penetrating oil
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors.
  2. Disconnect the electrical connectors from both sensors.
  3. Apply penetrating oil to the threads of the sensors and let it sit for a few minutes.
  4. Using the O2 sensor socket, remove the upstream sensor first, followed by the downstream sensor.
  5. Install the new sensors by threading them in and tightening to the manufacturer’s torque specifications (typically around 30 ft-lbs).
  6. Reconnect the electrical connectors securely.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust gasket
• Sub-steps:
  1. Locate the catalytic converter and inspect for damage or blockage.
  2. If replacement is needed, unbolt the catalytic converter from the exhaust manifold and the exhaust pipe. Use a penetrating oil if necessary.
  3. Remove the old catalytic converter and clean the mating surfaces.
  4. Install the new catalytic converter with a new gasket, ensuring proper alignment.
  5. Torque the bolts to the manufacturer’s specifications (typically around 30-40 ft-lbs).
  6. Reconnect any exhaust hangers and ensure a secure fit.

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals and ensure they are tight.
• Use the OBD-II scanner to clear the P0420 code and any related codes from the ECM.