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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, torque wrench.
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors on the exhaust system.
  2. Unplug the electrical connectors from both sensors.
  3. Use the O2 sensor socket to remove the sensors from the exhaust system.
  4. Install the new O2 sensors, ensuring they are torqued to the manufacturer's specifications (usually around 30-40 lb-ft).
  5. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if necessary).
• Sub-steps:
  1. Inspect the catalytic converter for signs of physical damage or blockage.
  2. If replacement is necessary, remove the exhaust pipes connected to the catalytic converter using a socket set.
  3. If the converter is welded, use an exhaust pipe cutter to remove it.
  4. Install the new catalytic converter, ensuring to align it correctly and secure with bolts.
  5. Torque bolts to manufacturer specifications (typically around 30-40 lb-ft).

4. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use an OBD-II scanner to clear the P0420 code.
• Perform a test drive to monitor system performance and ensure the check engine light does not reappear.