how to fix P0420 code on Honda Civic 11th Generation (2022-Present)

Solution

1. Preparation

• Gather tools and parts required for repair.
• Disconnect the battery to avoid electrical shorts during repairs.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream oxygen sensor:
  1. Locate the upstream O2 sensor (before the catalytic converter).
  2. Use the O2 sensor socket to unscrew the sensor from the exhaust manifold.
  3. Install the new oxygen sensor by threading it in by hand and then tightening it to the manufacturer's specifications (typically around 30-40 lb-ft).
• Repeat the process for the downstream oxygen sensor, located after the catalytic converter.

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

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if needed).
• Inspect the catalytic converter:
  1. Visually check for any obvious signs of damage or blockage.
  2. If damaged, proceed with removal.
• Remove the catalytic converter:
  1. Disconnect any exhaust hangers and heat shields.
  2. Use a socket set to unbolt the converter from the exhaust pipes.
  3. If necessary, use an exhaust pipe cutter to remove the converter.
• Install the new catalytic converter:
  1. Position the new catalytic converter in place.
  2. Bolt it securely using the appropriate torque specifications.
  3. Reattach any heat shields and exhaust hangers.

4. Reset the Check Engine Light

• Reconnect the battery.
• Use an OBD-II scanner to clear the trouble codes and reset the check engine light.