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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, and extension.
• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Disconnect the electrical connectors from both sensors.
  3. Use the O2 sensor socket to remove the sensors from the exhaust system.
  4. Install new oxygen sensors by threading them into place and tightening to the manufacturer's torque specifications (typically 30-35 ft-lbs).
  5. Reconnect the electrical connectors to the sensors.

3. Inspect or Replace the Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust gasket (if needed).
• Sub-steps:
  1. Locate the catalytic converter in the exhaust system.
  2. Remove any heat shields or brackets securing the converter.
  3. Disconnect the exhaust pipes from the catalytic converter by removing the bolts or nuts.
  4. Inspect the catalytic converter for any physical damage or blockage.
  5. If replacement is needed, install a new catalytic converter by reversing the removal steps, ensuring to use new gaskets if required and tightening bolts to the specified torque (usually around 30 ft-lbs).

4. Clear the Codes

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the battery if it was disconnected.
  2. Use the OBD-II scanner to clear the P0420 code from the ECU.
  3. Start the engine and allow it to reach operating temperature.