how to fix 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 flat surface and the engine is cool.
• Disconnect the battery to avoid electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Sub-steps:
  1. Locate the pre-catalytic and post-catalytic oxygen sensors.
  2. Disconnect the electrical connectors from each sensor.
  3. Remove the sensors using the O2 sensor socket.
  4. Install the new sensors by threading them into place and tightening to the manufacturer’s specified torque (usually around 30-40 ft-lbs).
  5. Reconnect the electrical connectors ensuring a secure fit.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, jack and jack stands, exhaust hanger removal tool, torque wrench.
• Sub-steps:
  1. Raise the vehicle and securely support it with jack stands.
  2. Locate the catalytic converter in the exhaust system.
  3. Remove the exhaust hangers using an exhaust hanger removal tool.
  4. Disconnect the catalytic converter from the exhaust pipes by removing the bolts or nuts with a socket set.
  5. Inspect the mounting surfaces for damage or corrosion.
  6. Install the new catalytic converter, ensuring proper alignment and secure it with bolts/nuts to the specified torque (usually around 25-35 ft-lbs).
  7. Reinstall the exhaust hangers.

4. Reset the Engine Control Unit (ECU)

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code from the ECU.
  3. Start the engine and let it idle for a few minutes.