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

Solution

1. Preparation

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

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench
• If oxygen sensor readings are faulty:
  1. Locate the upstream (pre-catalytic) oxygen sensor.
  2. Disconnect the electrical connector.
  3. Use the O2 sensor socket to remove the sensor.
  4. Install the new sensor by threading it into the exhaust pipe and tightening it to the manufacturer’s specifications (typically around 30 lb-ft).
  5. Reconnect the electrical connector.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, jack and jack stands, exhaust gasket
• If the catalytic converter is confirmed faulty:
  1. Raise the vehicle using a jack and secure it with jack stands.
  2. Remove any heat shields if present.
  3. Disconnect the exhaust pipes from the catalytic converter using the socket set.
  4. Carefully remove the catalytic converter from its mounting.
  5. Install the new catalytic converter, ensuring all gaskets are replaced.
  6. Reattach the exhaust pipes and tighten to manufacturer's specifications.

4. Reconnect Battery and Clear Codes

• After repairs are completed:
  1. Reconnect the battery terminals.
  2. Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.