how to fix the P0420 code on my Honda Civic 10th Generation (2016-2021)

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 battery terminal to prevent electrical issues.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench, anti-seize compound.
• Remove the pre-catalytic converter oxygen sensor:
  • Locate the sensor, disconnect the electrical connector, and use the O2 sensor socket to remove it.
  • Install the new oxygen sensor, applying anti-seize compound to the threads, and reconnect the electrical connector.
• Repeat the process for the post-catalytic converter oxygen sensor if necessary.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust gasket.
• Remove the catalytic converter:
  • Locate the catalytic converter under the vehicle, and disconnect the exhaust pipes using the socket set.
  • Remove any mounting bolts and detach the converter.
• Install the new catalytic converter:
  • Position the new catalytic converter and secure it with the mounting bolts.
  • Torque the bolts to the manufacturer’s specifications (consult the service manual for exact torque values).
• Replace any gaskets if necessary to ensure a proper seal.

4. Final Checks

• Reconnect the negative battery terminal.
• Clear the check engine codes using the OBD-II scanner.