how to fix P0420 code on 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 electrical shocks.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors.
  2. Remove the electrical connectors from the sensors.
  3. Use the O2 sensor socket to unscrew the sensors from the exhaust system.
  4. Install new oxygen sensors and tighten to manufacturer specifications (usually about 30 ft-lbs).
  5. Reconnect the electrical connectors.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, torque wrench, cutting tool (if necessary), exhaust gasket
• Sub-steps:
  1. Locate the catalytic converter beneath the vehicle.
  2. Remove any heat shields or brackets securing it.
  3. Unscrew the bolts connecting the catalytic converter to the exhaust system using the socket set.
  4. If the catalytic converter is welded in place, carefully cut it free with a cutting tool.
  5. Install a new catalytic converter with a new exhaust gasket, tightening bolts to the manufacturer's torque specifications (usually around 30 ft-lbs).
  6. Reattach any heat shields or brackets removed earlier.

4. Clear Trouble Codes

• Tools Required: OBD-II scanner
• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
  3. Start the engine and allow it to reach operating temperature.