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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery to prevent any electrical shorts.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• If the upstream or downstream oxygen sensors show faulty readings during the diagnostic phase, replace them.
  1. Locate the upstream and downstream oxygen sensors.
  2. Use the O2 sensor socket to remove the faulty sensor.
  3. Install the new sensor and tighten it to the manufacturer’s specified torque (typically 30-40 lb-ft).
  4. Reconnect the electrical connector.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Wrench set, socket set, exhaust jack or support, torque wrench.
• If the catalytic converter is damaged or clogged, replacement is necessary.
  1. Raise the vehicle securely using jack stands.
  2. Remove any heat shields or brackets securing the catalytic converter.
  3. Unbolt the catalytic converter from the exhaust manifold and the mid-pipe.
  4. Install the new catalytic converter, ensuring proper fitment.
  5. Torque the bolts to the manufacturer’s specifications.
  6. Reinstall any heat shields or brackets removed during disassembly.

4. Clear Codes and Test Drive

• Tools Required: OBD-II scanner.
• After replacing components, clear the error codes.
  1. Use the OBD-II scanner to erase the P0420 code.
  2. Start the engine and let it idle for a few minutes.
  3. Test drive the vehicle under various conditions to ensure the code does not reappear.