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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to ensure safety while working on electrical components.
• Raise the vehicle on jack stands for better access to the exhaust system.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, ratchet, torque wrench
• 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 their respective locations.
  4. Install new oxygen sensors by reversing the removal steps. Torque to manufacturer specifications (typically around 30 ft-lbs).

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, cutting tools (if needed), gaskets, exhaust sealant
• Sub-steps:
  1. Remove the exhaust heat shield if applicable to access the catalytic converter.
  2. Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe.
  3. Inspect the catalytic converter for any physical damage or signs of clogging.
  4. Install the new catalytic converter, ensuring proper alignment. Use new gaskets and apply exhaust sealant as necessary.
  5. Torque the bolts to manufacturer specifications.

4. Reassemble and Test

• Reinstall any components removed during the repair (e.g., heat shields).
• Reconnect the battery.
• Start the engine and allow it to reach operating temperature.